Chemistry » Electronic Structure of Atoms » Development of Quantum Theory

# Glossary of Words

## Glossary

### angular momentum quantum number (l)

quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum

### atomic orbital

mathematical function that describes the behavior of an electron in an atom (also called the wavefunction), it can be used to find the probability of locating an electron in a specific region around the nucleus, as well as other dynamical variables

### d orbital

region of space with high electron density that is either four lobed or contains a dumbbell and torus shape; describes orbitals with l = 2. An electron in this orbital is called a d electron

### degenerate orbitals

orbitals that have the same energy

### 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 function ψ

### f orbital

multilobed region of space with high electron density, describes orbitals with l = 3. An electron in this orbital is called an f electron

### 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 wave–particle duality

### magnetic quantum number (ml)

quantum number signifying the orientation of an atomic orbital around the nucleus; orbitals having different values of ml but the same subshell value of l have the same energy (are degenerate), but this degeneracy can be removed by application of an external magnetic field

### p orbital

dumbbell-shaped region of space with high electron density, describes orbitals with l = 1. An electron in this orbital is called a p electron

### Pauli exclusion principle

specifies that no two electrons in an atom can have the same value for all four quantum numbers

### principal quantum number (n)

quantum number specifying the shell an electron occupies in an atom

### quantum mechanics

field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter

### s orbital

spherical region of space with high electron density, describes orbitals with l = 0. An electron in this orbital is called an s electron

### shell

set of orbitals with the same principal quantum number, n

### spin quantum number (ms)

number specifying the electron spin direction, either $$+\phantom{\rule{0.2em}{0ex}}\frac{1}{2}$$ or $$-\phantom{\rule{0.2em}{0ex}}\frac{1}{2}$$

### subshell

set of orbitals in an atom with the same values of n and l

### wavefunction (ψ)

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

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