Applications of electronegativity
1) Nature of bond
The concept of electronegativity can be used to predict
whether the bond between similar or
dissimilar atoms is non-polar covalent bond, polar covalent bond (or) ionic bond.
1.
When XA = XB, i.e. XA- XB = 0, then A-B bond is non polar covalent bond or simply covalent bond and is represented as A-B. eg.
H-H bond in H2 molecule is a covalent bond and is represented as H-H
bond.
2.
When XA is slightly greater than XB, i.e. XA - XB is small,
the A-B bond is polar covalent bond
and is represented as Ad--Bd+ . e.g. The O-H
bonds in H2O molecule are polar covalent bonds and are represented as Od--Hd+, since XO> XH and XO - XH is small.
3.
When XA>> XB, i.e., XA - XB is very
large, A-B bond is more ionic or polar
bond and is represented as A--B+, Since XA>> XB. For example Na-Cl bond in Na Cl molecule is an ionic bond and is
represented as Na+Cl- (Here Cl = A and Na = B).
2) Percentage of ionic character in a polar covalent bond
Pauling estimated the percentage of ionic character in
various Ad--Bd+ polar covalent bonds from known (XA-XB) values and has derived the following
conclusions :
1.
When (XA-XB) = 1.7, the
amount of ionic character in Ad--Bd+ bond is 50% and that of covalent character is also 50%. Thus A-B
bond is 50% ionic and 50% covalent.
2.
When (XA-XB) < 1.7,
the amount of ionic character in Ad--Bd+ bond is less than 50% and that of covalent character is more than
50%. Thus Ad--Bd+ bond is predominantly covalent and hence is represented
as A-B.
When (XA-XB) > 1.7, the amount of ionic character in Ad--Bd+ bond is more than 50% and that of covalent character is less
than 50%. Hence Ad--Bd+ bond is
predominantly ionic and hence is represented as A-B+.
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