Nuclear & Particle Physics - Electron Configuration

The configuration of the potassium atom in its ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. Which of the following statement about potassium is true:

A. Its n = 3 shell is completely filled
B. Its 4s subshell is completely filled
C. Its least tightly bound electron has l = 4
D. Its atomic number is 17
E. Its electron charge distribution is spherically symmetrical

(GR8677 #30)

Solution:

A. FALSE.
n = 3 → l = 0, 1, 2 → s, p, d subshells, but the configuration does not have d subshells.

B. FALSE
4s subshell → for s subshell total electron should be 2 not 1.

C. FALSE
l = 0, 1, 2, 3, 4… correspond to s, p, d, f, g, … subshells, but the configuration does not have g subshells.

D. FALSE

the number of electrons in the configuration = 2+2+6+2+6+1 = 19, not 17.

E. TRUE
The single s-orbitals (l = 0) are shaped like spheres. For n = 1 the sphere is "solid" (it is most dense at the center and fades exponentially outwardly), but for n = 2 or more, each single s-orbital is composed of spherically symmetric surfaces which are nested shells (i.e., the "wave-structure" is radial, following a sinusoidal radial component as well).

The outermost electron shell (valence shell) is s¹ with n >1 and l = 0 → spherically symmetric.

Also note that Potassium has one outer electron, like Hydrogen. So it will also have a spherically symmetrical charge distribution.

Answer: E