correspond to the s, p, d, and f subshells, respectively. Just as with the principal quantum number,
energy increases as the azimuthal quantum number increases.
Within each subshell, there may be several orbitals. Orbitals are described by the magnetic
quantum number, ml, which ranges from –l to +l for a given subshell. Each type of atomic orbital
has a specific shape, which describes the probability of finding an electron in a given region of space.
An s-orbital is spherical and symmetrical, centered around the nucleus. A p-orbital is composed of
two lobes located symmetrically about the nucleus and contains a node—an area where the
probability of finding an electron is zero—at the nucleus. Picture the p-orbital as a dumbbell that
can be positioned in three different orientations, along the x-, y-, or z-axis. It should make sense that
there are three p-orbitals; the p subshell has the l-value of 1, so there are three possible values for
ml: –1, 0, and 1. The shapes of the first five s- and p-orbitals are shown in Figure 3.1. A d-orbital is
composed of four symmetrical lobes and contains two nodes. Four of the d-orbitals are clover-
shaped, and the fifth looks like a donut wrapped around the center of a p-orbital. Thankfully, the
multiple complex shapes of d- and f-orbitals are rarely encountered in organic chemistry. Each
orbital can hold two electrons, which are distinguished by the spin quantum number, ms. The only
values of ms are
Figure 3.1. The First Five Atomic OrbitalsMCAT Concept Check 3.1:
Before you move on, assess your understanding of the material with this question.Summarize the quantum numbers below. The first entry has been completed for
clarification.Symbol Name Describes... Organizational Level Possible Valuesn Principal QN Size Shell 1 to ∞l