Electronegativity is a measure of the tendency of a bonded atom to attract the bonding electrons to itself.
The table shows that
(1) electronegativity is higher for elements to the right and top of the periodic table
(2) metals are less electronegative than non-metals
Metals are referred to as electropositive.
(3) hydrogen has the lowest electronegativity of the elements commonly appearing in organic compounds.
The distribution of bonding electrons between bonded atoms depends on their relative electronegativities.
For bonded atoms where the difference in electronegativity is greater than 2.0, the bond is ionic.
If the difference in electronegativity between the bonded atoms is zero,
Red - more negative; green - equal sharing; bright blue - more positive
If the difference in electronegativity is more than 0 and less than 2.0, the bond is polar covalent.
| H 2.2 | He | |||||||
| Li 1.0 | Be 1.6 | B 2.0 | C 2.6 | N 3.0 | O 3.4 | F 4.0 | Ne | |
| Na 0.93 | Mg 1.3 | Al 1.6 | Si 1.9 | P 2.2 | S 2.6 | Cl 3.2 | Ar | |
| K 0.82 | Ca 1.0 | Ga 1.6 | Ge 1.8 | As 2.2 | Se 2.6 | Br 3.0 | Kr | |
| Rb 0.82 | Sr 0.95 | In 1.8 | Sn 2.0 | Sb 2.1 | Te 2.1 | I 2.7 | Xe | |
| Cs 0.79 | Ba 0.89 | Tl 1.6 | Pb 2.3 | Bi 2.0 | Po 2.0 | At | ||
The table shows that
(1) electronegativity is higher for elements to the right and top of the periodic table
(2) metals are less electronegative than non-metals
Metals are referred to as electropositive.
(3) hydrogen has the lowest electronegativity of the elements commonly appearing in organic compounds.
The distribution of bonding electrons between bonded atoms depends on their relative electronegativities.
For bonded atoms where the difference in electronegativity is greater than 2.0, the bond is ionic.
The atom of lower electronegativity exists as the cation (usually a metal such as Na+ in NaCl).
The atom of higher electronegativity exists as an anion (usually a non-metal such as Cl– in NaCl).
The atom of higher electronegativity exists as an anion (usually a non-metal such as Cl– in NaCl).
If the difference in electronegativity between the bonded atoms is zero,
the bond is covalent and the electron pair is shared equally as shown in the electrostatic potential map for chlorine.
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If the difference in electronegativity is more than 0 and less than 2.0, the bond is polar covalent.
Both atoms have a partial charge, the one of higher electronegativity being more negative (more red).
The relative partial changes at the bonded atoms depends on the difference in electronegativities.
See the electrostatic potential maps of HCl (electronegativity difference 1.0) and H2O (electronegativity difference 1.2).
The relative partial changes at the bonded atoms depends on the difference in electronegativities.
See the electrostatic potential maps of HCl (electronegativity difference 1.0) and H2O (electronegativity difference 1.2).