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The descent stage of the LM Eagle remains on the Moon. In 2009, the Lunar Reconnaissance Orbiter (LRO) imaged the various Apollo landing sites on the surface of the Moon, for the first time with sufficient resolution to see the descent stages of the lunar modules, scientific instruments, and foot trails made by the ast... | Apollo 11 | Wikipedia | 437 | 662 | https://en.wikipedia.org/wiki/Apollo%2011 | Technology | Crewed vehicles | null |
In November 1969, Nixon asked NASA to make up about 250 presentation Apollo 11 lunar sample displays for 135 nations, the fifty states of the United States and its possessions, and the United Nations. Each display included Moon dust from Apollo 11 and flags, including one of the Soviet Union, taken along by Apollo 11. ... | Apollo 11 | Wikipedia | 441 | 662 | https://en.wikipedia.org/wiki/Apollo%2011 | Technology | Crewed vehicles | null |
On July 20, 2009, Armstrong, Aldrin, and Collins met with President Barack Obama at the White House. "We expect that there is, as we speak, another generation of kids out there who are looking up at the sky and are going to be the next Armstrong, Collins, and Aldrin", Obama said. "We want to make sure that NASA is goin... | Apollo 11 | Wikipedia | 495 | 662 | https://en.wikipedia.org/wiki/Apollo%2011 | Technology | Crewed vehicles | null |
On July 19, 2019, the Google Doodle paid tribute to the Apollo 11 Moon Landing, complete with a link to an animated YouTube video with voiceover by astronaut Michael Collins.
Aldrin, Collins, and Armstrong's sons were hosted by President Donald Trump in the Oval Office.
Films and documentaries
Footprints on the Moo... | Apollo 11 | Wikipedia | 260 | 662 | https://en.wikipedia.org/wiki/Apollo%2011 | Technology | Crewed vehicles | null |
An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the term is sometimes applied to anyon... | Astronaut | Wikipedia | 468 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
, under the U.S. definition, 558 people qualify as having reached space, above altitude. Of eight X-15 pilots who exceeded in altitude, only one, Joseph A. Walker, exceeded 100 kilometers (about 62.1 miles) and he did it two times, becoming the first person in space twice. Space travelers have spent over 41,790 man-d... | Astronaut | Wikipedia | 511 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
NASA applies the term astronaut to any crew member aboard NASA spacecraft bound for Earth orbit or beyond. NASA also uses the term as a title for those selected to join its Astronaut Corps. The European Space Agency similarly uses the term astronaut for members of its Astronaut Corps.
Cosmonaut
By convention, an astr... | Astronaut | Wikipedia | 430 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
The term taikonaut is used by some English-language news media organizations for professional space travelers from China. The word has featured in the Longman and Oxford English dictionaries, and the term became more common in 2003 when China sent its first astronaut Yang Liwei into space aboard the Shenzhou 5 spacecra... | Astronaut | Wikipedia | 269 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
While no nation other than Russia (and previously the Soviet Union), the United States, and China have launched a crewed spacecraft, several other nations have sent people into space in cooperation with one of these countries, e.g. the Soviet-led Interkosmos program. Inspired partly by these missions, other synonyms fo... | Astronaut | Wikipedia | 294 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
As of 2021 in the United States, astronaut status is conferred on a person depending on the authorizing agency:
one who flies in a vehicle above for NASA or the military is considered an astronaut (with no qualifier)
one who flies in a vehicle to the International Space Station in a mission coordinated by NASA and R... | Astronaut | Wikipedia | 492 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
Cosmonaut Alexei Leonov was the first person to conduct an extravehicular activity (EVA), (commonly called a "spacewalk"), on 18 March 1965, on the Soviet Union's Voskhod 2 mission. This was followed two and a half months later by astronaut Ed White who made the first American EVA on NASA's Gemini 4 mission.
The first... | Astronaut | Wikipedia | 398 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
With the increase of seats on the Space Shuttle, the U.S. began taking international astronauts. In 1983, Ulf Merbold of West Germany became the first non-US citizen to fly in a US spacecraft. In 1984, Marc Garneau became the first of eight Canadian astronauts to fly in space (through 2010).
In 1985, Rodolfo Neri Vela ... | Astronaut | Wikipedia | 479 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
Civilian and non-government milestones
The first civilian in space was Valentina Tereshkova aboard Vostok 6 (she also became the first woman in space on that mission).
Tereshkova was only honorarily inducted into the USSR's Air Force, which did not accept female pilots at that time. A month later, Joseph Albert Walker ... | Astronaut | Wikipedia | 512 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
Training
The first NASA astronauts were selected for training in 1959. Early in the space program, military jet test piloting and engineering training were often cited as prerequisites for selection as an astronaut at NASA, although neither John Glenn nor Scott Carpenter (of the Mercury Seven) had any university degre... | Astronaut | Wikipedia | 488 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
Applicants must have a bachelor's degree with teaching experience, including work at the kindergarten through twelfth grade level. An advanced degree, such as a master's degree or a doctoral degree, is not required, but is strongly desired.
Mission Specialist Educators, or "Educator Astronauts", were first selected in ... | Astronaut | Wikipedia | 484 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
Over the last decade, flight surgeons and scientists at NASA have seen a pattern of vision problems in astronauts on long-duration space missions. The syndrome, known as visual impairment intracranial pressure (VIIP), has been reported in nearly two-thirds of space explorers after long periods spent aboard the Internat... | Astronaut | Wikipedia | 492 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
An astronaut on the International Space Station requires about mass of food per meal each day (inclusive of about packaging mass per meal).
Space Shuttle astronauts worked with nutritionists to select menus that appealed to their individual tastes. Five months before flight, menus were selected and analyzed for nutr... | Astronaut | Wikipedia | 505 | 664 | https://en.wikipedia.org/wiki/Astronaut | Technology | Basics_10 | null |
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The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitut... | Alkali metal | Wikipedia | 358 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
All of the discovered alkali metals occur in nature as their compounds: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity; francium occurs only in minute traces in nature as an intermedi... | Alkali metal | Wikipedia | 470 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Pure potassium was first isolated in 1807 in England by Humphry Davy, who derived it from caustic potash (KOH, potassium hydroxide) by the use of electrolysis of the molten salt with the newly invented voltaic pile. Previous attempts at electrolysis of the aqueous salt were unsuccessful due to potassium's extreme react... | Alkali metal | Wikipedia | 380 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Rubidium and caesium were the first elements to be discovered using the spectroscope, invented in 1859 by Robert Bunsen and Gustav Kirchhoff. The next year, they discovered caesium in the mineral water from Bad Dürkheim, Germany. Their discovery of rubidium came the following year in Heidelberg, Germany, finding it in ... | Alkali metal | Wikipedia | 457 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
There were at least four erroneous and incomplete discoveries before Marguerite Perey of the Curie Institute in Paris, France discovered francium in 1939 by purifying a sample of actinium-227, which had been reported to have a decay energy of 220 keV. However, Perey noticed decay particles with an energy level below 80... | Alkali metal | Wikipedia | 325 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
It is highly unlikely that this reaction will be able to create any atoms of ununennium in the near future, given the extremely difficult task of making sufficient amounts of einsteinium-254, which is favoured for production of ultraheavy elements because of its large mass, relatively long half-life of 270 days, and av... | Alkali metal | Wikipedia | 257 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The Oddo–Harkins rule holds that elements with even atomic numbers are more common that those with odd atomic numbers, with the exception of hydrogen. This rule argues that elements with odd atomic numbers have one unpaired proton and are more likely to capture another, thus increasing their atomic number. In elements ... | Alkali metal | Wikipedia | 472 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The alkali metals, due to their high reactivity, do not occur naturally in pure form in nature. They are lithophiles and therefore remain close to the Earth's surface because they combine readily with oxygen and so associate strongly with silica, forming relatively low-density minerals that do not sink down into the Ea... | Alkali metal | Wikipedia | 457 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Rubidium is approximately as abundant as zinc and more abundant than copper. It occurs naturally in the minerals leucite, pollucite, carnallite, zinnwaldite, and lepidolite, although none of these contain only rubidium and no other alkali metals. Caesium is more abundant than some commonly known elements, such as antim... | Alkali metal | Wikipedia | 505 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The alkali metals are more similar to each other than the elements in any other group are to each other. Indeed, the similarity is so great that it is quite difficult to separate potassium, rubidium, and caesium, due to their similar ionic radii; lithium and sodium are more distinct. For instance, when moving down the ... | Alkali metal | Wikipedia | 364 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
All the alkali metals are highly reactive and are never found in elemental forms in nature. Because of this, they are usually stored in mineral oil or kerosene (paraffin oil). They react aggressively with the halogens to form the alkali metal halides, which are white ionic crystalline compounds that are all soluble in ... | Alkali metal | Wikipedia | 256 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The second ionisation energy of all of the alkali metals is very high as it is in a full shell that is also closer to the nucleus; thus, they almost always lose a single electron, forming cations. The alkalides are an exception: they are unstable compounds which contain alkali metals in a −1 oxidation state, which is v... | Alkali metal | Wikipedia | 283 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
In aqueous solution, the alkali metal ions form aqua ions of the formula [M(H2O)n]+, where n is the solvation number. Their coordination numbers and shapes agree well with those expected from their ionic radii. In aqueous solution the water molecules directly attached to the metal ion are said to belong to the first co... | Alkali metal | Wikipedia | 461 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Lithium
The chemistry of lithium shows several differences from that of the rest of the group as the small Li+ cation polarises anions and gives its compounds a more covalent character. Lithium and magnesium have a diagonal relationship due to their similar atomic radii, so that they show some similarities. For exampl... | Alkali metal | Wikipedia | 271 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Francium
Francium is also predicted to show some differences due to its high atomic weight, causing its electrons to travel at considerable fractions of the speed of light and thus making relativistic effects more prominent. In contrast to the trend of decreasing electronegativities and ionisation energies of the alka... | Alkali metal | Wikipedia | 495 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Due to the great rarity of odd–odd nuclei, almost all the primordial isotopes of the alkali metals are odd–even (the exceptions being the light stable isotope lithium-6 and the long-lived radioisotope potassium-40). For a given odd mass number, there can be only a single beta-stable nuclide, since there is not a differ... | Alkali metal | Wikipedia | 436 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Caesium-137, with a half-life of 30.17 years, is one of the two principal medium-lived fission products, along with strontium-90, which are responsible for most of the radioactivity of spent nuclear fuel after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity stil... | Alkali metal | Wikipedia | 411 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The atomic radii of the alkali metals increase going down the group. Because of the shielding effect, when an atom has more than one electron shell, each electron feels electric repulsion from the other electrons as well as electric attraction from the nucleus. In the alkali metals, the outermost electron only feels a ... | Alkali metal | Wikipedia | 503 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The second ionisation energy of the alkali metals is much higher than the first as the second-most loosely held electron is part of a fully filled electron shell and is thus difficult to remove.
Reactivity
The reactivities of the alkali metals increase going down the group. This is the result of a combination of two ... | Alkali metal | Wikipedia | 465 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Because of the higher electronegativity of lithium, some of its compounds have a more covalent character. For example, lithium iodide (LiI) will dissolve in organic solvents, a property of most covalent compounds. Lithium fluoride (LiF) is the only alkali halide that is not soluble in water, and lithium hydroxide (LiOH... | Alkali metal | Wikipedia | 324 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Density
The alkali metals all have the same crystal structure (body-centred cubic) and thus the only relevant factors are the number of atoms that can fit into a certain volume and the mass of one of the atoms, since density is defined as mass per unit volume. The first factor depends on the volume of the atom and thu... | Alkali metal | Wikipedia | 384 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
All the alkali metals react vigorously or explosively with cold water, producing an aqueous solution of a strongly basic alkali metal hydroxide and releasing hydrogen gas. This reaction becomes more vigorous going down the group: lithium reacts steadily with effervescence, but sodium and potassium can ignite, and rubid... | Alkali metal | Wikipedia | 505 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The alkali metals form many intermetallic compounds with each other and the elements from groups 2 to 13 in the periodic table of varying stoichiometries, such as the sodium amalgams with mercury, including Na5Hg8 and Na3Hg. Some of these have ionic characteristics: taking the alloys with gold, the most electronegative... | Alkali metal | Wikipedia | 371 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Boron is a special case, being the only nonmetal in group 13. The alkali metal borides tend to be boron-rich, involving appreciable boron–boron bonding involving deltahedral structures, and are thermally unstable due to the alkali metals having a very high vapour pressure at elevated temperatures. This makes direct syn... | Alkali metal | Wikipedia | 238 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Lithium and sodium react with carbon to form acetylides, Li2C2 and Na2C2, which can also be obtained by reaction of the metal with acetylene. Potassium, rubidium, and caesium react with graphite; their atoms are intercalated between the hexagonal graphite layers, forming graphite intercalation compounds of formulae MC6... | Alkali metal | Wikipedia | 340 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
When the alkali metals react with the heavier elements in the carbon group (silicon, germanium, tin, and lead), ionic substances with cage-like structures are formed, such as the silicides M4Si4 (M = K, Rb, or Cs), which contains M+ and tetrahedral ions. The chemistry of alkali metal germanides, involving the germanid... | Alkali metal | Wikipedia | 267 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Lithium, the lightest of the alkali metals, is the only alkali metal which reacts with nitrogen at standard conditions, and its nitride is the only stable alkali metal nitride. Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N2) requires a lot of energy. The formation o... | Alkali metal | Wikipedia | 370 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
All the alkali metals react readily with phosphorus and arsenic to form phosphides and arsenides with the formula M3Pn (where M represents an alkali metal and Pn represents a pnictogen – phosphorus, arsenic, antimony, or bismuth). This is due to the greater size of the P3− and As3− ions, so that less lattice energy nee... | Alkali metal | Wikipedia | 392 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
All the alkali metals react vigorously with oxygen at standard conditions. They form various types of oxides, such as simple oxides (containing the O2− ion), peroxides (containing the ion, where there is a single bond between the two oxygen atoms), superoxides (containing the ion), and many others. Lithium burns in a... | Alkali metal | Wikipedia | 161 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The smaller alkali metals tend to polarise the larger anions (the peroxide and superoxide) due to their small size. This attracts the electrons in the more complex anions towards one of its constituent oxygen atoms, forming an oxide ion and an oxygen atom. This causes lithium to form the oxide exclusively on reaction w... | Alkali metal | Wikipedia | 444 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Rubidium and caesium can form a great variety of suboxides with the metals in formal oxidation states below +1. Rubidium can form Rb6O and Rb9O2 (copper-coloured) upon oxidation in air, while caesium forms an immense variety of oxides, such as the ozonide CsO3 and several brightly coloured suboxides, such as Cs7O (bron... | Alkali metal | Wikipedia | 446 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The alkali metals are among the most electropositive elements on the periodic table and thus tend to bond ionically to the most electronegative elements on the periodic table, the halogens (fluorine, chlorine, bromine, iodine, and astatine), forming salts known as the alkali metal halides. The reaction is very vigorous... | Alkali metal | Wikipedia | 470 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Alkali metal cations do not usually form coordination complexes with simple Lewis bases due to their low charge of just +1 and their relatively large size; thus the Li+ ion forms most complexes and the heavier alkali metal ions form less and less (though exceptions occur for weak complexes). Lithium in particular has a... | Alkali metal | Wikipedia | 272 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Ammonia solutions
The alkali metals dissolve slowly in liquid ammonia, forming ammoniacal solutions of solvated metal cation M+ and solvated electron e−, which react to form hydrogen gas and the alkali metal amide (MNH2, where M represents an alkali metal): this was first noted by Humphry Davy in 1809 and rediscovered... | Alkali metal | Wikipedia | 366 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Being the smallest alkali metal, lithium forms the widest variety of and most stable organometallic compounds, which are bonded covalently. Organolithium compounds are electrically non-conducting volatile solids or liquids that melt at low temperatures, and tend to form oligomers with the structure (RLi)x where R is th... | Alkali metal | Wikipedia | 493 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Alkyllithiums and aryllithiums may also react with N,N-disubstituted amides to give aldehydes and ketones, and symmetrical ketones by reacting with carbon monoxide. They thermally decompose to eliminate a β-hydrogen, producing alkenes and lithium hydride: another route is the reaction of ethers with alkyl- and aryllith... | Alkali metal | Wikipedia | 501 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Alkyl and aryl derivatives of sodium and potassium tend to react with air. They cause the cleavage of ethers, generating alkoxides. Unlike alkyllithium compounds, alkylsodiums and alkylpotassiums cannot be made by reacting the metals with alkyl halides because Wurtz coupling occurs:
RM + R'X → R–R' + MX
As such, they ... | Alkali metal | Wikipedia | 454 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The alkali metal peroxides are ionic compounds that are unstable in water. The peroxide anion is weakly bound to the cation, and it is hydrolysed, forming stronger covalent bonds.
Na2O2 + 2H2O → 2NaOH + H2O2
The other oxygen compounds are also unstable in water.
2KO2 + 2H2O → 2KOH + H2O2 + O2
Li2O + H2O → 2LiOH
Reacti... | Alkali metal | Wikipedia | 457 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
On reaction with water, they generate hydroxide ions and hydrogen gas. This reaction is vigorous and highly exothermic and the hydrogen resulted may ignite in air or even explode in the case of Rb and Cs.
Na + H2O → NaOH + 1/2H2
Reaction with other salts
The alkali metals are very good reducing agents. They can reduc... | Alkali metal | Wikipedia | 309 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Although francium is the heaviest alkali metal that has been discovered, there has been some theoretical work predicting the physical and chemical characteristics of hypothetical heavier alkali metals. Being the first period 8 element, the undiscovered element ununennium (element 119) is predicted to be the next alkali... | Alkali metal | Wikipedia | 363 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The stabilisation of ununennium's valence electron and thus the contraction of the 8s orbital cause its atomic radius to be lowered to 240 pm, very close to that of rubidium (247 pm), so that the chemistry of ununennium in the +1 oxidation state should be more similar to the chemistry of rubidium than to that of franci... | Alkali metal | Wikipedia | 263 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Not as much work has been done predicting the properties of the alkali metals beyond ununennium. Although a simple extrapolation of the periodic table (by the Aufbau principle) would put element 169, unhexennium, under ununennium, Dirac-Fock calculations predict that the next element after ununennium with alkali-metal-... | Alkali metal | Wikipedia | 423 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The probable properties of further alkali metals beyond unsepttrium have not been explored yet as of 2019, and they may or may not be able to exist. In periods 8 and above of the periodic table, relativistic and shell-structure effects become so strong that extrapolations from lighter congeners become completely inaccu... | Alkali metal | Wikipedia | 501 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The first ionisation energy of hydrogen (1312.0 kJ/mol) is much higher than that of the alkali metals. As only one additional electron is required to fill in the outermost shell of the hydrogen atom, hydrogen often behaves like a halogen, forming the negative hydride ion, and is very occasionally considered to be a hal... | Alkali metal | Wikipedia | 295 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The 1s1 electron configuration of hydrogen, while analogous to that of the alkali metals (ns1), is unique because there is no 1p subshell. Hence it can lose an electron to form the hydron H+, or gain one to form the hydride ion H−. In the former case it resembles superficially the alkali metals; in the latter case, the... | Alkali metal | Wikipedia | 376 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The ammonium ion () has very similar properties to the heavier alkali metals, acting as an alkali metal intermediate between potassium and rubidium, and is often considered a close relative. For example, most alkali metal salts are soluble in water, a property which ammonium salts share. Ammonium is expected to behave ... | Alkali metal | Wikipedia | 380 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Cobaltocene and derivatives
Cobaltocene, Co(C5H5)2, is a metallocene, the cobalt analogue of ferrocene. It is a dark purple solid. Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes, such as its very stable relative, ferrocene, in accordance with the 18-electron rule.... | Alkali metal | Wikipedia | 278 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Thallium is the heaviest stable element in group 13 of the periodic table. At the bottom of the periodic table, the inert-pair effect is quite strong, because of the relativistic stabilisation of the 6s orbital and the decreasing bond energy as the atoms increase in size so that the amount of energy released in forming... | Alkali metal | Wikipedia | 425 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The group 11 metals (or coinage metals), copper, silver, and gold, are typically categorised as transition metals given they can form ions with incomplete d-shells. Physically, they have the relatively low melting points and high electronegativity values associated with post-transition metals. "The filled d subshell an... | Alkali metal | Wikipedia | 426 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The coinage metals were traditionally regarded as a subdivision of the alkali metal group, due to them sharing the characteristic s1 electron configuration of the alkali metals (group 1: p6s1; group 11: d10s1). However, the similarities are largely confined to the stoichiometries of the +1 compounds of both groups, and... | Alkali metal | Wikipedia | 340 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The production of pure alkali metals is somewhat complicated due to their extreme reactivity with commonly used substances, such as water. From their silicate ores, all the stable alkali metals may be obtained the same way: sulfuric acid is first used to dissolve the desired alkali metal ion and aluminium(III) ions fro... | Alkali metal | Wikipedia | 353 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Sodium occurs mostly in seawater and dried seabed, but is now produced through electrolysis of sodium chloride by lowering the melting point of the substance to below 700 °C through the use of a Downs cell. Extremely pure sodium can be produced through the thermal decomposition of sodium azide. Potassium occurs in many... | Alkali metal | Wikipedia | 381 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Rubidium is the 16th most abundant element in the earth's crust; however, it is quite rare. Some minerals found in North America, South Africa, Russia, and Canada contain rubidium. Some potassium minerals (lepidolites, biotites, feldspar, carnallite) contain it, together with caesium. Pollucite, carnallite, leucite, an... | Alkali metal | Wikipedia | 477 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
As a result of its extreme rarity in nature, most francium is synthesised in the nuclear reaction 197Au + 18O → 210Fr + 5 n, yielding francium-209, francium-210, and francium-211. The greatest quantity of francium ever assembled to date is about 300,000 neutral atoms, which were synthesised using the nuclear reaction g... | Alkali metal | Wikipedia | 465 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Potassium compounds are often used as fertilisers as potassium is an important element for plant nutrition. Potassium hydroxide is a very strong base, and is used to control the pH of various substances. Potassium nitrate and potassium permanganate are often used as powerful oxidising agents. Potassium superoxide is us... | Alkali metal | Wikipedia | 397 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Experiments are usually conducted using only small quantities of a few grams in a fume hood. Small quantities of lithium may be disposed of by reaction with cool water, but the heavier alkali metals should be dissolved in the less reactive isopropanol. The alkali metals must be stored under mineral oil or an inert atmo... | Alkali metal | Wikipedia | 369 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Sodium and potassium occur in all known biological systems, generally functioning as electrolytes inside and outside cells. Sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH; the minimum physiological requirement for sodium is 500 milligrams per day. Sodium chloride... | Alkali metal | Wikipedia | 326 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Due to their similar atomic radii, rubidium and caesium in the body mimic potassium and are taken up similarly. Rubidium has no known biological role, but may help stimulate metabolism, and, similarly to caesium, replace potassium in the body causing potassium deficiency. Partial substitution is quite possible and rath... | Alkali metal | Wikipedia | 389 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
Radioisotopes of caesium require special precautions: the improper handling of caesium-137 gamma ray sources can lead to release of this radioisotope and radiation injuries. Perhaps the best-known case is the Goiânia accident of 1987, in which an improperly-disposed-of radiation therapy system from an abandoned clinic ... | Alkali metal | Wikipedia | 202 | 666 | https://en.wikipedia.org/wiki/Alkali%20metal | Physical sciences | Chemical element groups | null |
The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (np) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used... | Atomic number | Wikipedia | 498 | 673 | https://en.wikipedia.org/wiki/Atomic%20number | Physical sciences | Basics_4 | null |
In 1913, Antonius van den Broek proposed that the electric charge of an atomic nucleus, expressed as a multiplier of the elementary charge, was equal to the element's sequential position on the periodic table. Ernest Rutherford, in various articles in which he discussed van den Broek's idea, used the term "atomic numbe... | Atomic number | Wikipedia | 446 | 673 | https://en.wikipedia.org/wiki/Atomic%20number | Physical sciences | Basics_4 | null |
In 1911, Ernest Rutherford gave a model of the atom in which a central nucleus held most of the atom's mass and a positive charge which, in units of the electron's charge, was to be approximately equal to half of the atom's atomic weight, expressed in numbers of hydrogen atoms. This central charge would thus be approxi... | Atomic number | Wikipedia | 486 | 673 | https://en.wikipedia.org/wiki/Atomic%20number | Physical sciences | Basics_4 | null |
Missing elements
After Moseley's death in 1915, the atomic numbers of all known elements from hydrogen to uranium (Z = 92) were examined by his method. There were seven elements (with Z < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and... | Atomic number | Wikipedia | 490 | 673 | https://en.wikipedia.org/wiki/Atomic%20number | Physical sciences | Basics_4 | null |
Discovery of the neutron makes Z the proton number
All consideration of nuclear electrons ended with James Chadwick's discovery of the neutron in 1932. An atom of gold now was seen as containing 118 neutrons rather than 118 nuclear electrons, and its positive nuclear charge now was realized to come entirely from a con... | Atomic number | Wikipedia | 375 | 673 | https://en.wikipedia.org/wiki/Atomic%20number | Physical sciences | Basics_4 | null |
Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to dev... | Anatomy | Wikipedia | 358 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Derived from the Greek anatomē "dissection" (from anatémnō "I cut up, cut open" from ἀνά aná "up", and τέμνω témnō "I cut"), anatomy is the scientific study of the structure of organisms including their systems, organs and tissues. It includes the appearance and position of the various parts, the materials from which... | Anatomy | Wikipedia | 445 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
The term "anatomy" is commonly taken to refer to human anatomy. However, substantially similar structures and tissues are found throughout the rest of the animal kingdom, and the term also includes the anatomy of other animals. The term zootomy is also sometimes used to specifically refer to non-human animals. The stru... | Anatomy | Wikipedia | 410 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Connective tissue
Connective tissues are fibrous and made up of cells scattered among inorganic material called the extracellular matrix. Often called fascia (from the Latin "fascia," meaning "band" or "bandage"), connective tissues give shape to organs and holds them in place. The main types are loose connective tissu... | Anatomy | Wikipedia | 471 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Muscle cells (myocytes) form the active contractile tissue of the body. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Sm... | Anatomy | Wikipedia | 488 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
All vertebrates have a similar basic body plan and at some point in their lives, mostly in the embryonic stage, share the major chordate characteristics: a stiffening rod, the notochord; a dorsal hollow tube of nervous material, the neural tube; pharyngeal arches; and a tail posterior to the anus. The spinal cord is pr... | Anatomy | Wikipedia | 327 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish. The main skeletal element is the vertebral col... | Anatomy | Wikipedia | 510 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Amphibians are a class of animals comprising frogs, salamanders and caecilians. They are tetrapods, but the caecilians and a few species of salamander have either no limbs or their limbs are much reduced in size. Their main bones are hollow and lightweight and are fully ossified and the vertebrae interlock with each ot... | Anatomy | Wikipedia | 380 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Reptiles are a class of animals comprising turtles, tuataras, lizards, snakes and crocodiles. They are tetrapods, but the snakes and a few species of lizard either have no limbs or their limbs are much reduced in size. Their bones are better ossified and their skeletons stronger than those of amphibians. The teeth are ... | Anatomy | Wikipedia | 484 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Lizards have skulls with only one fenestra on each side, the lower bar of bone below the second fenestra having been lost. This results in the jaws being less rigidly attached which allows the mouth to open wider. Lizards are mostly quadrupeds, with the trunk held off the ground by short, sideways-facing legs, but a fe... | Anatomy | Wikipedia | 410 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Birds are tetrapods but though their hind limbs are used for walking or hopping, their front limbs are wings covered with feathers and adapted for flight. Birds are endothermic, have a high metabolic rate, a light skeletal system and powerful muscles. The long bones are thin, hollow and very light. Air sac extensions f... | Anatomy | Wikipedia | 504 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Mammals are amniotes, and most are viviparous, giving birth to live young. Exceptions to this are the egg-laying monotremes, the platypus and the echidnas of Australia. Most other mammals have a placenta through which the developing foetus obtains nourishment, but in marsupials, the foetal stage is very short and the i... | Anatomy | Wikipedia | 439 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Invertebrates constitute a vast array of living organisms ranging from the simplest unicellular eukaryotes such as Paramecium to such complex multicellular animals as the octopus, lobster and dragonfly. They constitute about 95% of the animal species. By definition, none of these creatures has a backbone. The cells of ... | Anatomy | Wikipedia | 471 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Marcello Malpighi, the father of microscopical anatomy, discovered that plants had tubules similar to those he saw in insects like the silk worm. He observed that when a ring-like portion of bark was removed on a trunk a swelling occurred in the tissues above the ring, and he unmistakably interpreted this as growth sti... | Anatomy | Wikipedia | 412 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Other branches of anatomy
Surface anatomy is important as the study of anatomical landmarks that can be readily seen from the exterior contours of the body. It enables medics and veterinarians to gauge the position and anatomy of the associated deeper structures. Superficial is a directional term that indicates that ... | Anatomy | Wikipedia | 361 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Some of the most striking advances in early anatomy and physiology took place in Hellenistic Alexandria. Two of the most famous anatomists and physiologists of the third century were Herophilus and Erasistratus. These two physicians helped pioneer human dissection for medical research, using the cadavers of condemned c... | Anatomy | Wikipedia | 484 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Incredible feats were made during the third century BCE in both the digestive and reproductive systems. Herophilus discovered and described not only the salivary glands but also the small intestine and liver. He showed that the uterus is a hollow organ and described the ovaries and uterine tubes. He recognized that spe... | Anatomy | Wikipedia | 504 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
Andreas Vesalius (1514–1564), professor of anatomy at the University of Padua, is considered the founder of modern human anatomy. Originally from Brabant, Vesalius published the influential book De humani corporis fabrica ("the structure of the human body"), a large format book in seven volumes, in 1543. The accurate a... | Anatomy | Wikipedia | 339 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
The teaching of anatomy in Britain was transformed by Sir John Struthers, Regius Professor of Anatomy at the University of Aberdeen from 1863 to 1889. He was responsible for setting up the system of three years of "pre-clinical" academic teaching in the sciences underlying medicine, including especially anatomy. This s... | Anatomy | Wikipedia | 505 | 674 | https://en.wikipedia.org/wiki/Anatomy | Biology and health sciences | Biology | null |
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