Term

Definition
The arrangement of electrons of an atom or molecule. 


Term
electromagnetic radiation (radiant energy) 

Definition
A form of energy that has wave characteristics and that propagates through a vacuum at the characteristic speed of 3.00 × 10^{8} m/s. 


Term

Definition
The distance between identical points on successive waves. 


Term

Definition
The number of times per second that one complete wavelength passes a given point. 


Term

Definition
The smallest increment of radiant energy that may be absorbed or emitted; the magnitude of radiant energy is hv. 


Term

Definition
The constant that relates the energy and frequency of a photon, E = hv. Its value is 6.626 × 10^{34} Js. 


Term

Definition
The smallest increment (a quantum) of radiant energy; a photon of light with frequency v has an energy equal to hv. 


Term

Definition
The distribution among various wavelengths of the radiant energy emitted or absorbed by an object. 


Term

Definition
A spectrum that contains radiation distributed over all wavelengths. 


Term

Definition
A spectrum that contains radiation at only certain specific wavelengths. 


Term

Definition
The lowestenergy, or most stable, state. 


Term

Definition
A higher state than the ground state. 


Term

Definition
The term used to describe the wave characteristics of a particle. 


Term

Definition
The product of the mass, m, and velocity, v, of a particle. 


Term

Definition
A principle stating there is an inherent uncertainty in the precision with which we can simultaneously specify the position and momentum of a particle. This uncertainty is significant only for extremely small particles, such as electrons. 


Term

Definition
A mathematical description of an allowed energy state (an orbital) for an electron in the quantum mechanical model of the atom; it is usually symbolized by the Greek letter Ψ. 


Term
probability density (Ψ^{2}) 

Definition
A value that represents the probability that an electron will be found at a given point in space. 


Term

Definition
The probability of finding an electron at any particular point in an atom; this probability is equal to Ψ^{2}, the square of the wave function. 


Term

Definition
An allowed energy state of an electron in the quantum mechanical model of the atom; the term orbital is also used to describe the spatial distribution of the electron. An orbital is defined by the values of three quantum numbers: n, l, and m_{1}. 


Term

Definition
A collection of orbitals that have the same value of n. For example, the orbitals with n = 3 (the 3s, 3p, and 3d orbitals) comprise the third shell. 


Term

Definition
One or more orbitals with the same set of quantum numbers n and l. For example, we speak of the 2p subshell (n = 2, l = 1), which is composed of three orbitals (2p_{x}, 2p_{y}, and 2p_{z}). 


Term

Definition
A locus of points in an atom at which the electron density is zero. For example, the node in a 2s orbital is a spherical surface. 


Term

Definition
Having the same energy (in several orbitals). 


Term

Definition
A property of the electron that makes it behave as though it were a tiny magnet. The electron behaves as if it were spinning on its axis; electron spin is quantized. 


Term
spin magnetic quantum number (m_{s}) 

Definition
A quantum number associated with the electron spin; it may have values of +½ or ½. 


Term
Pauli exclusion principle 

Definition
A rule stating that no two electrons in an atom may have the same four quantum numbers (n, l, m_{l}, and m_{s}). As a consequence of this principle, there can be no more than two electrons in any one atomic orbital. 


Term

Definition
A particular arrangement of electrons in the orbitals of an atom. 


Term

Definition
A rule stating that electrons occupy degenerate orbitals in such a way as to maximize the number of electrons with the same spin. In other words, each orbital has one electron placed in it before pairing of electrons in orbitals occurs. Note that this rule applies only to orbitals that are degenerate, which means that they have the same energy. 


Term

Definition
The electrons that are not in the outermost shell of an atom. 


Term

Definition
The outermost electrons of an atom; those that occupy orbitals not occupied in the nearest noblegas element of lower atomic number. The valence electrons are the ones the atoms uses in bonding. 


Term
transition elements (transition metals) 

Definition
Elements in which the d orbitals are partially occupied. 


Term
lanthanide (or rare earth) element 

Definition
Element in which the 4f subshell is only partially occupied. 


Term

Definition
Element in which the 5f orbitals are only partially occupied. 


Term
representative (or maingroup) element 

Definition
Element in which the s and p orbitals are partially occupied. 


Term

Definition
Lanthanide and actinide elements in which the 4f or 5f orbitals are partially occupied. 

