Shielding or screening effect

1. Shielding or Screening
Dr. Mithil Fal Desai
Shree Mallikarjun and Shri Chetan
Manju Desai College Canacona Goa

2. Effective nuclear charge (Zeff)
Zeff = Z – σ
Zeff = Z – S
σ or S is shieling constant

3. Shielding

4. Screening

5. Shielding
The reduction of the true nuclear charge to
effective nuclear charge by other electrons is
called shielding.

6. Energy of electron, atomic number,
principal quantum number
Energy of electron is a
function of Z2/n2
Does this mean that energy
required to remove
electron from an atom
continuously increases
with the atomic number?
Z n Z2/n2
1 1 1
2 1 4
3 2 2.25
4 2 4
5 2 6.25
6 2 9
7 2 12.25
8 2 16
9 2 20.25

7. Why this is not true?
A) Average radius of 2s
orbital is greater
than 1s.
A) 2s electrons are
repelled by 1s
electrons.
Nucleus
e-

8. Remember!
• Shielding and screening decreases the true nuclear
charge.
• Shielding constant can be measured following the
Slater rules