Chapter 9:Glossary
By convention an asterisk indicates that there is a complimentary entry in Appendix A – Readying Mathematical Concepts.
Angular momentum quantum number *
Also known as the orbital quantum number or the azimuthal quantum number, and denoted by 
, this describes the electron subshell and gives the magnitude of the orbital angular momentum.
Anti-commutator *
An operation of two operators 
defined as: 
.
Anti-commutation *
A set of fermionic annihilation operators and creation operators that act on local electron modes can be defined that satisfy anti-commutation relations.
Atom
A basic particle that composes a chemical element. It consists of a nucleus surrounded by moving electrons arranged in orbitals that describe their positions in terms of probabilities. The atom has no overall electric charge.
Atomic number
A number that identifies an atom by the number of protons/electrons in the atom being specified.