Shielding or screening effect

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 ( Z eff ) Z eff = Z – σ Z eff = 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 Z 2 /n 2 Does this mean that energy required to remove electron from an atom continuously increases with the atomic number ? Z n Z 2 /n 2 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? Average radius of 2s orbital is greater than 1s. 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