Electronic Structure of Atoms

Electron configurations and the periodic table


Electron Configurations and the Periodic Table

The periodic table is structured so that elements with the same type of valence electron configuration are arranged in columns.

These two groups comprise the main-group elements

Important facts to remember:

  1. 2, 6, 10 and 14 are the number of electrons that can fill the s, p, d and f subshells (the l=0,1,2,3 azimuthal quantum number)
  2. The 1s subshell is the first s subshell, the 2p is the first p subshell (n=2, l=1, 3d is the first d subshell, and the 4f is the first f subshell

What is the electron configuration for the element Niobium? (41)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d3

Niobium is actually:

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d4

The reason is that the 5s and 4d energy levels are quite close and certain electronic arrangements can result in the levels being slightly different than expected.

What is the electron configuration of the element Nickel? (28)

1s2 2s2 2p6 3s2 3p6 4s2 3d8

What is the electron configuration for Nickel in terms of the nearest noble gas?

[Ar] 4s2 3d8

How would the last valence orbital be filled?


1996 Michael Blaber