This document discusses bond polarity and electronegativity. It defines electronegativity as an atom's ability to attract electrons in a chemical bond. Bonds between atoms with similar electronegativities are nonpolar, while bonds between atoms with differing electronegativities are polar. The document introduces the Pauling scale for measuring electronegativity values of different elements. It also provides a method for calculating bond polarity by taking the difference between the electronegativities of the bonded atoms. The degree of polarity is used to classify bonds as nonpolar, moderately polar, very polar, or ionic. Examples are given to demonstrate how to determine bond type based on electronegativity differences.

1. Bond Polarity and
Electronegativity
MARIZA R MAPALO
MED CHEM

2. Learning Objectives
•To define electronegativity and
bond polarity
•To calculate the percent ionic
character of a covalent polar
bond

3. Bond Polarity
• is a useful concept for
describing the sharing of
electrons between atoms
within a covalent bond

4. Bond Polarity
•A nonpolar covalent bond is one in
which the electrons are
shared equally between two atoms.
•A polar covalent bond is one in
which one atom has a greater
attraction for the electrons than the
other atom.

5. Electronegativity (EN)
•defined as the relative ability of
an atom to attract electrons to
itself in a chemical compound.
•represented by the Greek
letter chi, χ, pronounced “ky”

6. Electronegativity (EN)
•Elements with high electronegativities tend
to acquire electrons in chemical reactions and
are found in the upper right corner of the
periodic table.
•Elements with low electronegativities tend
to lose electrons in chemical reactions and are
found in the lower left corner of the periodic
table.

7. Electronegativity (EN)
Electronegativity is a function of:
1.the atom's ionization energy (how
strongly the atom holds on to its own
electrons) and
2.the atom's electron affinity (how
strongly the atom attracts other
electrons).

8. Electronegativity (EN)
The Pauling Electronegativity Scale
The original electronegativity scale, developed in the
1930s by Linus Pauling (1901– 1994) was based on
measurements of the strengths of covalent bonds
between different elements. Pauling arbitrarily set
the electronegativity of fluorine at 4.0 (although
today it has been refined to 3.98), thereby creating
a scale in which all elements have values between 0
and 4.0.

9. The Pauling Electronegativity Scale

10. Activity
Direction:
Determine the EN value of the following
molecules. Type your answers on the chat
box
1. H
2. Mg
3. O
4. F
2.2
1.3
3.4
3.9

11. Electronegativity (EN)
•The polarity of a bond—the extent to
which it is polar—is determined largely
by the relative electronegativities of
the bonded atoms.
•Electronegativity (χ) was defined as
the ability of an atom in a molecule or
an ion to attract electrons to itself.

12. Electronegativity (EN)
•A bond is nonpolar if the bonded atoms have equal
electronegativities. If the electronegativities of the
bonded atoms are not equal, however, the bond
is polarized toward the more electronegative atom.
•A bond in which the electronegativity of B (χB) is
greater than the electronegativity of A (χA), for
example, is indicated with the partial negative
charge on the more electronegative atom:

13. Electronegativity (EN)
A bond in which the electronegativity of B (χB) is
greater than the electronegativity of A (χA), for
example, is indicated with the partial negative
charge on the more electronegative atom:

14. Electronegativity (EN)
One way of estimating the ionic
character of a bond—that is, the
magnitude of the charge separation in a
polar covalent bond—is to calculate the
difference in electronegativity between
the two atoms:
Δχ = χB − χA.

15. Electronegativity (EN)
One way of estimating the ionic
character of a bond—that is, the
magnitude of the charge separation in a
polar covalent bond—is to calculate the
difference in electronegativity between
the two atoms:
Δχ = χB − χA.

16. Classification of Bonds
Less than 0.4 non-polar covalent
0.4 - 1.0 moderately polar covalent
1.0 - 2.0 very polar covalent
2.0 above ionic

17. Examples
Molecules Electronegativity
Values
Electronegativity
Difference
Bond Type
H----Cl 0.96
H: 2.20
Cl: 3.16
MOderately
Polar
Covalent
Less than 0.4 non-polar covalent
0.4 to 1.0 moderately polar covalent
1.0-2.0 very polar covalent
2.0 above ionic

18. The H-Cl bond can thus be
represented as:
H Cl H Cl
or
•The 'd+' and 'd-' symbols indicate partial positive and negative
charges.
•The arrow indicates the "pull" of electrons off the hydrogen and
towards the more electronegative atom

19. Activity
Molecules Electronegativity
Values
Electronegativity
Difference
Bond Type
H-H
H-I
Ca-O

20. References
https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-
_The_Central_Science_(Brown_et_al.)/08%3A_Basic_Concepts_of_Chemical_Bonding/
8.04%3A_Bond_Polarity_and_Electronegativity
http://www.mikeblaber.org/oldwine/chm1045/
notes/Bonding/Polarity/Bond05.htm