Factors Affecting Electronegativity

1. Factors Affecting Electronegativity

2. Introduction. • Is a chemical property that describes the ability of an atom (or, more rarely, a functional group) to attract electrons (or electron density) towards itself.

3. Factors Affecting Atomic size • As the size of the atom decreases it has greater tendency to attract the bonding electrons towards itself. Therefore smaller atoms have higher electronegativity values than the larger ones

4. Factors. Ionisation energy and electron affinity • Higher Ionisation energy and electron affinity lead to higher electronegativity. Number and nature of atoms • The electronegativity depends on the number and nature of atoms bonded to it.

5. Factors. Factors. Type of hybridization • The electronegativity increases with the increase in 's' character in the hybrid orbital. This is because the 's' orbitals being more near to the nucleus have greater tendency to attract the shared pair of electron.

6. Factors. Charge on the ion • A cation has high electronegativity while an anion has less electronegativity than its parent atom. A cation with a higher positive charge is more electronegative.

7. Factors. Variation along a period • As the nuclear charge increases from going left to right in a period because the electrons enter the same shell, the shielding is less effective. Thus the increased nuclear charge attract the shared pair of electrons more strongly resulting in higher electronegativity from going left to right in a period. Variation down the group • Electronegativity decreases down the group because the atomic size increases. The larger the size of the atom the lesser the tendency to attract the shared pair of electrons.

8. Calculation of eletronegativity • The most commonly used method of calculation is that originally proposed by Pauling. • This gives a dimensionless quantity, commonly referred to as the Pauling scale, on a relative scale running from 0.7 to 4.0 (hydrogen = 2.2).

9. Trend of Electronegativity

10. Trend. • In general, electronegativity increases on passing from left to right along a period, and decreases on descending a group. • Hence, fluorine is undoubtedly the most electronegative of the elements while caesium is the least electronegative, at least of those elements for which substantial data is available. • There are some exceptions to this general rule. • Gallium and germanium have higher electronegativities than aluminium and silicon respectively

11. Videos • http://www.youtube.com/watch?v=WyfwRPBw62s&feature=related

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