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Trends in Electronegativity

Key Concepts

  • In 1932 Linus Pauling defined electronegativity as the power of an atom in a molecule to attract electrons to itself.

  • Pauling devised a numerical electronegativity scale, based on bond energies.

  • In general, electronegativities decrease down a Group of the Periodic Table.

  • In general, electronegativities increase going from left to right across a Period of the Periodic Table.

Animated Tutorial

Trends in Electronegativities in Groups of the Periodic Table

In general, the electronegativities of the elements in a Group decrease as you go down the group from top to bottom.
As the atomic radius increases and the number of completed electron shells (energy levels) increases going down the group, the power of the atom's nucleus to attract electrons to itself decreases.

Group 1 (IA, Alkali Metals)

Element Atomic
Number
(Z)
Symbol Electronegativity Trend
lithium 3 Li 0.98 (highest)
|
Electronegativity decreases down Group 1 as
  • atomic radius increases
  • number of inner electron shells increases.
sodium 11 Na 0.93 |
potassium 19 K 0.82 |
rubidium 37 Rb 0.82 |
cesium 55 Cs 0.79 |
francium 87 Fr 0.7 \/
(lowest)

Group 17 (VIIA, Halogens)

Element Atomic
Number
(Z)
Symbol Electronegativity Trend
fluorine 9 F 3.98 (highest)
|
Electronegativity decreases down Group 17 as
  • atomic radius increases
  • number of inner electron shells increases.
chlorine 17 Cl 3.16 |
bromine 35 Br 2.96 |
iodine 53 I 2.66 |
astatine 85 At 2.2 |
\/
(lowest)

Trends in Electronegativity in Periods of the Periodic Table

In general, electronegativities of the elements in the same Period increases as you go from left to right across the period.
As the nuclear charge increases and the atomic radius decreases across a period, the power of the atom's nucleus to attract electrons to itself increases.

Period 2

Element Li Be B C N O F
Atomic Number (Z) 3 4 5 6 7 8 9
Electronegativity 0.98 1.57 2.04 2.55 3.04 3.44 3.98
General Trend (lowest)- ----- ----- ----- ----- ----> (highest)
Electronegativity increases across Period 2 as nuclear charge increases and atomic radius decreases.

Period 3

Element Na Mg Al Si P S Cl
Atomic Number (Z) 11 12 13 14 15 16 17
Electronegativity 0.93 1.31 1.61 1.9 2.19 2.58 3.16
General Trend (lowest)- ----- ----- ----- ----- ----> (highest)
Electronegativity increases across Period 3 as nuclear charge increases and atomic radius decreases.


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