What is the effective nuclear charge experienced by the valence electrons in each of the following?

a) Ca

Answer

Zeff = +2

Explanation

If we complete the table below for a calcium atom

Element

Nuclear
Charge

Electron
Configuration

Inner Core
Electrons

Valence
Electrons

Effective Nuclear
Charge

Ca

20

1s22s22p63s23p64s2

18

2

+2

The effective nuclear charge is determined by subtracting from the number of protons in the nucleus (Z), the number of inner core (I.C.) electrons that shield the valence electron from the nucleus.

Zeff = Z - I.C.

For calcium

Zeff = 20 - 18 = +2