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ground state : state in which the electrons in an atom, ion, or molecule have the lowest energy possible | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
group : vertical column of the periodic table | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
halogen : element in group 17 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Heisenberg uncertainty principle : rule stating that it is impossible to exactly determine both certain conjugate dynamical properties such as the momentum and the position of a particle at the same time. The uncertainty principle is a consequence of quantum particles exhibiting waveâparticle duality | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
hertz (Hz) : the unit of frequency, which is the number of cycles per second, sâ1 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Hundâs rule : every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
inert gas : (also, noble gas) element in group 18 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
inner transition metal : (also, lanthanide or actinide) element in the bottom two rows; if in the first row, also called lanthanide, or if in the second row, also called actinide | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
intensity : property of wave-propagated energy related to the amplitude of the wave, such as brightness of light or loudness of sound | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
interference pattern : pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
ionic bond : electrostatic forces of attraction between the oppositely charged ions of an ionic compound | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
ionic compound : compound composed of cations and anions combined in ratios, yielding an electrically neutral substance | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
ionization energy : energy required to remove an electron from a gaseous atom or ion | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
isoelectronic : group of ions or atoms that have identical electron configurations | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
lanthanide : inner transition metal in the top of the bottom two rows of the periodic table | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
line spectrum : electromagnetic radiation emitted at discrete wavelengths by a specific atom (or atoms) in an excited state | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
magnetic quantum number (ml) : quantum number signifying the orientation of an atomic orbital around the nucleus | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
main-group element : (also, representative element) element in groups 1, 2, and 13â18 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
metal : element that is shiny, malleable, good conductor of heat and electricity | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
metalloid : element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
molecular compound : (also, covalent 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 |
monatomic ion : ion composed of a single atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
noble gas : (also, inert gas) element in group 18 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
node : any point of a standing wave with zero amplitude | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
nonmetal : element that appears dull, poor conductor of heat and electricity | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
orbital diagram : pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
oxyanion : polyatomic anion composed of a central atom bonded to oxygen atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
porbital : dumbbell-shaped region of space with high electron density, describes orbitals withl= 1 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Pauli exclusion principle : specifies that no two electrons in an atom can have the same value for all four quantum numbers | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
period : (also, series) horizontal row of the periodic table | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
periodic law : properties of the elements are periodic function of their atomic numbers | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
periodic table : table of the elements that places elements with similar chemical properties close together | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
photon : smallest possible packet of electromagnetic radiation, a particle of light | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
pnictogen : element in group 15 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
polyatomic ion : ion composed of more than one atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
principal quantum number (n) : quantum number specifying the shell an electron occupies in an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
quantization : limitation of some property to specific discrete values, not continuous | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
quantum mechanics : field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
quantum number : number having only specific allowed values and used to characterize the arrangement of electrons in an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
representative element : (also, main-group element) element in columns 1, 2, and 12â18 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
sorbital : spherical region of space with high electron density, describes orbitals withl= 0 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
secondary (angular momentum) quantum number (l) : quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
series : (also, period) horizontal row of the period table | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
shell : atomic orbitals with the same principal quantum number,n | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
spin quantum number (ms) : number specifying the electron spin direction, either+12+12orâ12â12 | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
standing wave : (also, stationary wave) localized wave phenomenon characterized by discrete wavelengths determined by the boundary conditions used to generate the waves; standing waves are inherently quantized | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
subshell : atomic orbitals with the same values ofnandl | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
transition metal : element in groups 3â12 (more strictly defined, 3â11; see chapter on transition metals and coordination chemistry) | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
valence electrons : electrons in the high energy outer shell(s) of an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
valence shell : high energy outer shell(s) of an atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
wave : oscillation of a property over time or space; can transport energy from one point to another | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
wave-particle duality : observation that elementary particles can exhibit both wave-like and particle-like properties | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
wavefunction (Ï) : mathematical description of an atomic orbital that describes the shape of the orbital; it can be used to calculate the probability of finding the electron at any given location in the orbital, as well as dynamical variables such as the energy and the angular momentum | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
wavelength (λ) : distance between two consecutive peaks or troughs in a wave | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-key-terms |
Light and other forms of electromagnetic radiation move through a vacuum with a constant speed,c, of 2.998ÃÃ108m sâ1. This radiation shows wavelike behavior, which can be characterized by a frequency,ν, and a wavelength,λ, such thatc=λν. Light is an example of a travelling wave. Other important wave phenomena i... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Bohr incorporated Planckâs and Einsteinâs quantization ideas into a model of the hydrogen atom that resolved the paradox of atom stability and discrete spectra. The Bohr model of the hydrogen atom explains the connection between the quantization of photons and the quantized emission from atoms. Bohr described the h... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Macroscopic objects act as particles. Microscopic objects (such as electrons) have properties of both a particle and a wave. Their exact trajectories cannot be determined. The quantum mechanical model of atoms describes the three-dimensional position of the electron in aprobabilisticmanner according to a mathematical f... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
An atomic orbital is characterized by three quantum numbers. The principal quantum number,n, can be any positive integer. The general region for value of energy of the orbital and the average distance of an electron from the nucleus are related ton. Orbitals having the same value ofnare said to be in the same shell. Th... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
The relative energy of the subshells determine the order in which atomic orbitals are filled (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on). Electron configurations and orbital diagrams can be determined by applying the Pauli exclusion principle (no two electrons can have the same set of four quantum numbers) and Hundâs... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Electrons in the outermost orbitals, called valence electrons, are responsible for most of the chemical behavior of elements. In the periodic table, elements with analogous valence electron configurations usually occur within the same group. There are some exceptions to the predicted filling order, particularly when ha... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Electron configurations allow us to understand many periodic trends. Covalent radius increases as we move down a group because thenlevel (orbital size) increases. Covalent radius mostly decreases as we move left to right across a period because the effective nuclear charge experienced by the electrons increases, and th... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
The discovery of the periodic recurrence of similar properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing atomic number in rows known as periods and columns known as groups. Elements in the same group of the periodic table have similar chem... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Metals (particularly those in groups 1 and 2) tend to lose the number of electrons that would leave them with the same number of electrons as in the preceding noble gas in the periodic table. By this means, a positively charged ion is formed. Similarly, nonmetals (especially those in groups 16 and 17, and, to a lesser ... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
Compounds that contain ions are called ionic compounds. Ionic compounds generally form from metals and nonmetals. Compounds that do not contain ions, but instead consist of atoms bonded tightly together in molecules (uncharged groups of atoms that behave as a single unit), are called covalent compounds. Covalent compou... | https://openstax.org/books/chemistry-atoms-first-2e/pages/3-summary |
formal charge = # valence shell electrons (free atom) â # lone pair electrons â 1 2 # bonding electrons formal charge = # valence shell electrons (free atom) â # lone pair electrons â 1 2 # bonding electrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-equations |
axial position : location in a trigonal bipyramidal geometry in which there is another atom at a 180° angle and the equatorial positions are at a 90° angle | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
binary acid : compound that contains hydrogen and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ions when dissolved in water) | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
binary compound : compound containing two different elements. | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
bond angle : angle between any two covalent bonds that share a common atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
bond dipole moment : separation of charge in a bond that depends on the difference in electronegativity and the bond distance represented by partial charges or a vector | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
bond distance : (also, bond length) distance between the nuclei of two bonded atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
bond length : distance between the nuclei of two bonded atoms at which the lowest potential energy is achieved | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
covalent bond : bond formed when electrons are shared between atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
dipole moment : property of a molecule that describes the separation of charge determined by the sum of the individual bond moments based on the molecular structure | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
double bond : covalent bond in which two pairs of electrons are shared between two atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
electron-pair geometry : arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons) | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
electronegativity : tendency of an atom to attract electrons in a bond to itself | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
equatorial position : one of the three positions in a trigonal bipyramidal geometry with 120° angles between them; the axial positions are located at a 90° angle | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
formal charge : charge that would result on an atom by taking the number of valence electrons on the neutral atom and subtracting the nonbonding electrons and the number of bonds (one-half of the bonding electrons) | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
free radical : molecule that contains an odd number of electrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
hypervalent molecule : molecule containing at least one main group element that has more than eight electrons in its valence shell | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
inert pair effect : tendency of heavy atoms to form ions in which their valenceselectrons are not lost | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
ionic bond : strong electrostatic force of attraction between cations and anions in an ionic compound | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
Lewis structure : diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
Lewis symbol : symbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
linear : shape in which two outside groups are placed on opposite sides of a central atom | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
lone pair : two (a pair of) valence electrons that are not used to form a covalent bond | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
molecular structure : arrangement of atoms in a molecule or ion | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
molecular structure : structure that includes only the placement of the atoms in the molecule | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
nomenclature : system of rules for naming objects of interest | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
octahedral : shape in which six outside groups are placed around a central atom such that a three-dimensional shape is generated with four groups forming a square and the other two forming the apex of two pyramids, one above and one below the square plane | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
octet rule : guideline that states main group atoms will form structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected by the bond | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
oxyacid : compound that contains hydrogen, oxygen, and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ions when dissolved in water) | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
polar covalent bond : covalent bond between atoms of different electronegativities; a covalent bond with a positive end and a negative end | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
polar molecule : (also, dipole) molecule with an overall dipole moment | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
pure covalent bond : (also, nonpolar covalent bond) covalent bond between atoms of identical electronegativities | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
resonance : situation in which one Lewis structure is insufficient to describe the bonding in a molecule and the average of multiple structures is observed | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
resonance forms : two or more Lewis structures that have the same arrangement of atoms but different arrangements of electrons | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
resonance hybrid : average of the resonance forms shown by the individual Lewis structures | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
single bond : bond in which a single pair of electrons is shared between two atoms | https://openstax.org/books/chemistry-atoms-first-2e/pages/4-key-terms |
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