3.1 Atomic Orbitals and Quantum Numbers

LEARNING GOALS

After   Chapter 3.1,    you will    be  able    to:

Describe    the four    quantum numbers,    n,  l,  ml, and ms

Provide ranges  of  possible    values  for each    quantum number

Bonding occurs in the outermost electron shell of atoms, so an understanding of bonding is
contingent on understanding the organization of electrons in an atom. Quantum numbers are
discussed in detail in Chapter 1 of MCAT General Chemistry Review, and are briefly summarized here.

The first three quantum numbers, n, l, and ml, describe the size, shape, number, and orientation of
atomic orbitals an element possesses. The principal quantum number, n, corresponds to the
energy level of a given electron in an atom and is essentially a measure of size. The smaller the
number, the closer the shell is to the nucleus, and the lower its energy. The possible values of n
range from 1 to ∞, although the MCAT only tests on n-values up to 7.

BRIDGE

Recall  from    Chapter 1   of  MCAT    General Chemistry   Review  that    quantum numbers describe

the location    of  an  electron    within  an  atom    and that    each    electron    has a   unique  combination

of  quantum numbers according   to  the Pauli   exclusion   principle.

Within each electron shell, there can be several subshells. Subshells are described by the azimuthal
quantum number, l, which ranges from 0 to n – 1 for a given energy shell. The l-values 0, 1, 2, and 3