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mass : fundamental property indicating amount of matter | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
matter : anything that occupies space and has mass | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
meter (m) : standard metric and SI unit of length; 1 m = approximately 1.094 yards | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
microscopic domain : realm of things that are much too small to be sensed directly | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
milliliter (mL) : 1/1,000 of a liter; equal to 1 cm3 | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
mixture : matter that can be separated into its components by physical means | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
molecule : bonded collection of two or more atoms of the same or different elements | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
physical change : change in the state or properties of matter that does not involve a change in its chemical composition | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
physical property : characteristic of matter that is not associated with any change in its chemical composition | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
plasma : gaseous state of matter containing a large number of electrically charged atoms and/or molecules | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
precision : how closely a measurement matches the same measurement when repeated | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
pure substance : homogeneous substance that has a constant composition | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
rounding : procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
scientific method : path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
second (s) : SI unit of time | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
SI units (International System of Units) : standards fixed by international agreement in the International System of Units (Le Système International dâUnités) | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
significant figures : (also, significant digits) all of the measured digits in a determination, including the uncertain last digit | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
solid : state of matter that is rigid, has a definite shape, and has a fairly constant volume | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
symbolic domain : specialized language used to represent components of the macroscopic and microscopic domains, such as chemical symbols, chemical formulas, chemical equations, graphs, drawings, and calculations | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
temperature : intensive property representing the hotness or coldness of matter | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
theory : well-substantiated, comprehensive, testable explanation of a particular aspect of nature | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
uncertainty : estimate of amount by which measurement differs from true value | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
unit : standard of comparison for measurements | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
unit conversion factor : ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
volume : amount of space occupied by an object | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
weight : force that gravity exerts on an object | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-key-terms |
Chemistry deals with the composition, structure, and properties of matter, and the ways by which various forms of matter may be interconverted. Thus, it occupies a central place in the study and practice of science and technology. Chemists use the scientific method to perform experiments, pose hypotheses, and formulate... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
Matter is anything that occupies space and has mass. The basic building block of matter is the atom, the smallest unit of an element that can enter into combinations with atoms of the same or other elements. In many substances, atoms are combined into molecules. On earth, matter commonly exists in three states: solids,... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
All substances have distinct physical and chemical properties, and may undergo physical or chemical changes. Physical properties, such as hardness and boiling point, and physical changes, such as melting or freezing, do not involve a change in the composition of matter. Chemical properties, such flammability and acidit... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
Measurable properties fall into one of two categories. Extensive properties depend on the amount of matter present, for example, the mass of gold. Intensive properties do not depend on the amount of matter present, for example, the density of gold. Heat is an example of an extensive property, and temperature is an exam... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
Measurements provide quantitative information that is critical in studying and practicing chemistry. Each measurement has an amount, a unit for comparison, and an uncertainty. Measurements can be represented in either decimal or scientific notation. Scientists primarily use SI (International System) units such as meter... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
Quantities can be defined or measured. Measured quantities have an associated uncertainty that is represented by the number of significant figures in the quantityâs number. The uncertainty of a calculated quantity depends on the uncertainties in the quantities used in the calculation and is reflected in how the value... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
Measurements are made using a variety of units. It is often useful or necessary to convert a measured quantity from one unit into another. These conversions are accomplished using unit conversion factors, which are derived by simple applications of a mathematical approach called the factor-label method or dimensional a... | https://openstax.org/books/chemistry-atoms-first-2e/pages/1-summary |
average mass = â i ( fractional abundance à isotopic mass ) i average mass = â i ( fractional abundance à isotopic mass ) i | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-equations |
alpha particle (α particle) : positively charged particle consisting of two protons and two neutrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
anion : negatively charged atom or molecule (contains more electrons than protons) | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
atomic mass : average mass of atoms of an element, expressed in amu | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
atomic mass unit (amu) : (also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to112112of the mass of a12C atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
atomic number (Z) : number of protons in the nucleus of an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
cation : positively charged atom or molecule (contains fewer electrons than protons) | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
chemical symbol : one-, two-, or three-letter abbreviation used to represent an element or its atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
Dalton (Da) : alternative unit equivalent to the atomic mass unit | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
Daltonâs atomic theory : set of postulates that established the fundamental properties of atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
electron : negatively charged, subatomic particle of relatively low mass located outside the nucleus | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
empirical formula : formula showing the composition of a compound given as the simplest whole-number ratio of atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
fundamental unit of charge : (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602ÃÃ10â19C | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
ion : electrically charged atom or molecule (contains unequal numbers of protons and electrons) | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
isomers : compounds with the same chemical formula but different structures | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
isotopes : atoms that contain the same number of protons but different numbers of neutrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
law of constant composition : (also, law of definite proportions) all samples of a pure compound contain the same elements in the same proportions by mass | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
law of definite proportions : (also, law of constant composition) all samples of a pure compound contain the same elements in the same proportions by mass | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
law of multiple proportions : when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small whole numbers | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
mass number (A) : sum of the numbers of neutrons and protons in the nucleus of an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
molecular formula : formula indicating the composition of a molecule of a compound and giving the actual number of atoms of each element in a molecule of the compound. | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
neutron : uncharged, subatomic particle located in the nucleus | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
nucleus : massive, positively charged center of an atom made up of protons and neutrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
proton : positively charged, subatomic particle located in the nucleus | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
spatial isomers : compounds in which the relative orientations of the atoms in space differ | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
structural formula : shows the atoms in a molecule and how they are connected | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
structural isomer : one of two substances that have the same molecular formula but different physical and chemical properties because their atoms are bonded differently | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
unified atomic mass unit (u) : alternative unit equivalent to the atomic mass unit | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-key-terms |
The ancient Greeks proposed that matter consists of extremely small particles called atoms. Dalton postulated that each element has a characteristic type of atom that differs in properties from atoms of all other elements, and that atoms of different elements can combine in fixed, small, whole-number ratios to form com... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
Although no one has actually seen the inside of an atom, experiments have demonstrated much about atomic structure. Thomsonâs cathode ray tube showed that atoms contain small, negatively charged particles called electrons. Millikan discovered that there is a fundamental electric chargeâthe charge of an electron. Ru... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
An atom consists of a small, positively charged nucleus surrounded by electrons. The nucleus contains protons and neutrons; its diameter is about 100,000 times smaller than that of the atom. The mass of one atom is usually expressed in atomic mass units (amu), which is referred to as the atomic mass. An amu is defined ... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
Protons are relatively heavy particles with a charge of 1+ and a mass of 1.0073 amu. Neutrons are relatively heavy particles with no charge and a mass of 1.0087 amu. Electrons are light particles with a charge of 1â and a mass of 0.00055 amu. The number of protons in the nucleus is called the atomic number (Z) and is... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
Isotopes of an element are atoms with the same atomic number but different mass numbers; isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus. When a naturally occurring element is composed of several isotopes, the atomic mass of the element represents the average ... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
A molecular formula uses chemical symbols and subscripts to indicate the exact numbers of different atoms in a molecule or compound. An empirical formula gives the simplest, whole-number ratio of atoms in a compound. A structural formula indicates the bonding arrangement of the atoms in the molecule. Ball-and-stick and... | https://openstax.org/books/chemistry-atoms-first-2e/pages/2-summary |
c = λν | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
E = h ν = h c λ , E = h ν = h c λ , where h = 6.626 à à 10 â34 J s | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
1 λ = R â ( 1 n 1 2 â 1 n 2 2 ) 1 λ = R â ( 1 n 1 2 â 1 n 2 2 ) | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
E n = â k Z 2 n 2 , n = 1 , 2 , 3 , ⦠E n = â k Z 2 n 2 , n = 1 , 2 , 3 , ⦠| https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
Î E = k Z 2 ( 1 n 1 2 â 1 n 2 2 ) Î E = k Z 2 ( 1 n 1 2 â 1 n 2 2 ) | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
r = n 2 Z a 0 r = n 2 Z a 0 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-equations |
actinide : inner transition metal in the bottom of the bottom two rows of the periodic table | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
alkali metal : element in group 1 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
alkaline earth metal : element in group 2 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
amplitude : extent of the displacement caused by a wave | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
atomic orbital : mathematical function that describes the behavior of an electron in an atom (also called the wavefunction) | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Aufbau principle : procedure in which the electron configuration of the elements is determined by âbuildingâ them in order of atomic numbers, adding one proton to the nucleus and one electron to the proper subshell at a time | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
blackbody : idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Bohrâs model of the hydrogen atom : structural model in which an electron moves around the nucleus only in circular orbits, each with a specific allowed radius | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
chalcogen : element in group 16 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
continuous spectrum : electromagnetic radiation given off in an unbroken series of wavelengths (e.g., white light from the sun) | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
core electron : electron in an atom that occupies the orbitals of the inner shells | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
covalent bond : attractive force between the nuclei of a moleculeâs atoms and pairs of electrons between the atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
covalent compound : (also, molecular compound) composed of molecules formed by atoms of two or more different elements | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
covalent radius : one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
dorbital : region of space with high electron density that is either four lobed or contains a dumbbell and torus shape; describes orbitals withl= 2. | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
degenerate orbitals : orbitals that have the same energy | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
effective nuclear charge : charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
electromagnetic radiation : energy transmitted by waves that have an electric-field component and a magnetic-field component | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
electromagnetic spectrum : range of energies that electromagnetic radiation can comprise, including radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
electron affinity : energy change associated with addition of an electron to a gaseous atom or ion | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
electron configuration : listing that identifies the electron occupancy of an atomâs shells and subshells | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
electron density : a measure of the probability of locating an electron in a particular region of space, it is equal to the squared absolute value of the wave functionÏ | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
endothermic : processes that increase the energy of an atom and involve the absorption of light | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
excited state : state having an energy greater than the ground-state energy | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
exothermic : processes that decrease the energy of an atom and involve the emission of light | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
forbital : multilobed region of space with high electron density, describes orbitals withl= 3 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
frequency (ν) : number of wave cycles (peaks or troughs) that pass a specified point in space per unit time | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
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