Allred and Rochow Electronegativity

1. Allred and Rochow
Electronegativity
Dr. Mithil Fal Desai
Shree Mallikarjun and Shri
Chetan Manju Desai College
Canacona Goa

3. Electronegativity is an ‘attractive force between a
nucleus and an electron at a distance equal to
the covalent radius.’
Allred and Rochow definition of
Electronegativity
𝐹 =
𝑒2 𝑍 𝑒𝑓𝑓
𝑟2
Where, e is charge on electron, r is
the covalent radius and Zeff is the
effective nuclear charge.
What are
the factors
that affect
Zeff?

4. Factors affecting Zeff
• Size of an atom
• The total nuclear charge (Z).
• The Screening and Shielding of the inner shell
electrons and neighboring electrons of the same
shell.
• The extent of penetration of outermost electron
into the charge cloud.

5. F to χ
𝐹 =
𝑒2 𝑍 𝑒𝑓𝑓
𝑟2
𝐹 = 0.744 +
0.359 𝑍 𝑒𝑓𝑓
𝑟2
χ 2.18 2.19 2.24 2.27 2.35
Molybdenu
m oxidation
state
+2 +3 +4 +5 +6