Question

What is the effective nuclear charge experienced by the 2p and 3p electrons of a chlorine atom, respectively?

Answer 1

The effective nuclear charge may be defined as the actual nuclear charge (Z) minus the screening effect caused by the electrons intervening between the nucleus and valence electron.

Effective nuclear charge, Z* = Z - σ    Where, Z= Atomic number, σ = Shielding or screening constant.

σ can be found out for an electron using slators rules.

Slater's Rules:

1) Write the electron configuration for the atom using the following design;

(1s)(2s,2p)(3s,3p) (3d) (4s,4p) (4d) (4f) (5s,5p)

2) Any electrons to the right of the electron of interest contributes no shielding.

3) All other electrons in the same group as the electron of interest shield to an extent of 0.35 nuclear charge units

4) If the electron of interest is an s or p electron: All electrons with one less value of the principal quantum number shield to an extent of 0.85 units of nuclear charge. All electrons with two less values of the principal quantum number shield to an extent of 1.00 units.

5) If the electron of interest is an d or f electron: All electrons to the left shield to an extent of 1.00 units of nuclear charge.

6) Sum the shielding amounts from steps 2 through 5 and subtract from the nuclear charge value to obtain the effective nuclear charge.

So coming to the given question , effective nuclear charge experienced by the 2p and 3p electrons of a chlorine atom,

electronic configuration of chlorine atom is 1s² 2s² 2p⁶ 3s² 3p⁵

σ for 2p = 0.35 x 7 + 0.85 x 2 = 4.14

σ for 2p = 0.35 x 6 + 0.85 x 8 + 1 x 2 = 10.9

Z for chlorine = 17

Z* for 2p electron = 17 - 4.14 = 12.86

Z* for 3p electron = 17 - 10.9 = 6.1