The Foundations of Chemistry

by the values of n,
, and m
, has a capacity of two electrons. Electrons are negatively

charged, and they behave as though they were spinning about axes through their centers,
so they act like tiny magnets. The motions of electrons produce magnetic fields, and these
can interact with one another. Two electrons in the same orbital having opposite msvalues
are said to be spin-paired,or simply paired(Figure 5-27).
Let us summarize, in tabular form, some of the information we have developed to this
point. The principal quantum number nindicates the main shell. The number of subshells
per shell is equal to n, the number of atomic orbitals per shell is n^2 , and the maximum
number of electrons per shell is 2n^2 , because each atomic orbital can hold two electrons.

Figure 5-26 Shapes and

approximate relative sizes of several

orbitals in an atom.

5-16 Atomic Orbitals 213

Figure 5-25 Relative directional character of forbitals. The seven orbitals are shown
within cubes as an aid to visualization.

z

y

x fz^3 – – zr^2

fxyz

3

5

fy (^3) – –^3 yr 2
5
fy (x (^2) – z (^2) )
fx (z (^2) – y (^2) ) fz (x (^2) – y (^2) )
fx (^3) – –^3 xr 2
5
1 s 2 s 2 p
3 s 3 p