Electron Configuration Notation?

Question

INTRO:

QUESTION:

1) What is wrong with the notation 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^2 for germanium (atomic number 32)?

A) The 4s subshell should appear before the 3d subshell.

B) The 3p subshell should have more than 6 electrons.

C) The 3d subshell can hold only 8 electrons.

D) The 4d subshell should receive electrons before the 4p subshell.

*answer definitely not C

2) Write the electron configuration for the Na^+ ion, which has ten electrons...

3) Write the electron configuration for the Br^- ion, which has thirty-six electrons...

Answer 1

1) The answer is A.  The energy of the 4s shell is lower than that of the 3d shell, so the 4s shell will be filled first.

2) Na+ : 1s2 2s2 2p6

3) Br- : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

Hope that helps