Quantum numbers
MCAT glossary · MCAT
Definition
N (principal, energy level), l (azimuthal, subshell shape: s/p/d/f), ml (magnetic, orbital orientation), ms (spin, ± 1/2).
Quantum numbers in plain English
Quantum numbers are like a four-part mailing address that pins down exactly where an electron lives around an atom and how it's spinning. The first, n, is the floor number — the main energy level and roughly how far out the electron is. The second, l, is the room's shape (labeled s, p, d, f), and the third, m_l, is which way that room is turned in space. The last, m_s, is the electron's own spin, either +1/2 or -1/2 — and because no two electrons in an atom can share all four numbers, each gets its own unique address.
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