- The principal quantum number describes the energy level or the shell in which an electron is found. Hence, given the principal quantum number, we can deduce the energy of a given electron -- A matches with P.
- The azimuthal quantum number is also called the secondary quantum number or the angular...

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- The principal quantum number describes the energy level or the shell in which an electron is found. Hence, given the principal quantum number, we can deduce the energy of a given electron -- A matches with P.
- The azimuthal quantum number is also called the secondary quantum number or the angular quantum number. It describes the subshell to which a given electron belongs. Its values ranges from 0 to (n-1) where n is the principal quantum number. Each of these numbers correspond to an orbital type (e.g. 0 to s, 1 to p, etc.) and describe the orbital angular momentum. -- B matches with Q.
- The magnetic quantum number describes the projection of the orbital - or sometimes the 'orientation' of the orbital. For instance, the s-type orbital is spherical and only has one possible orientation, while p-type has three (dumbbell-shaped) and each lie on one of the axes. In a box diagram, the number of possible magnetic quantum number gives the number of 'boxes' or orbitals -- D matches R.
- The spin quantum number describes the instrinsic angular momentum of an electron (spinning on its axis). Due to Pauli's Exclusion Principle, only a maximum of 2 electrons can occupy an orbital. The spin quantum number takes on two possible values +1/2 or -1/2 (or 'spin' and 'opposite spin' respectively). Hence, if you're first electron is always designated as 'spin' or +1/2 and the second as 'opposite' or -1/2, then this tell us the number of electrons in a given orbital -- C matches S.

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