Chemistry Honors
Name: ____________________________
Bond type, as defined by electronegativity
Date: ___________________ Period: ___
Questions to think about, and answer after this activity…
1. How do differences in electronegativity determine whether two atoms will transfer or share
electrons, to form a bond?
2. If electrons are shared between two atoms, are they always shared equally?
Electronegativity (Χ) is a measure of an atom’s ability to attract electrons. Below is a table of
electronegativities.
Most active nonmetals have very high electronegativities; they strongly attract a valence electron to
form a stable octet.
Most active metals have very low electronegativities; they easily lose a valence electron to form a
stable octet.
Two atoms will form an ionic bond, if the atoms have a large difference in electronegativity values.
But how great does the difference have to be?
We will define an ionic bond as having an electronegativity difference of 1.7 or greater.
With this difference, the electron is considered to be completely transferred from one atom to the
other. This occurs between a metal and a nonmetal element.
When two atoms with similar electronegativities bond, there is a “tug of war” for valence electrons.
Neither atom can “win” the fight. The result is a bond where 2 valence electrons (one from each
atom) are held in-between the atoms, and each atom considers the 2 “shared” electrons as belonging
to their octet.
Atoms with similar Χ values share valence electrons, and we call this a covalent bond.
Nonmetals will covalently bond with each other.
When two atoms share a pair of electrons to form a covalent bond, the pair of electrons may be
shared equally or unequally, depending on the degree of electronegativity difference between the two
atoms. This requires us to define two types of covalent bonds:
A. Polar covalent bond: electrons are shared unequally, resulting in partial charges on each
atom.
The shared electrons will spend more time closer to the more electronegative atom
causing it to have a partial negative charge (δ-), while the other atom has a partial
positive charge (δ+).
B. Nonpolar covalent bond: electrons are shared equally, resulting in no partial charges.
What electronegativity difference defines an “equal sharing” of electrons? 0.4 or less.
The following table summarizes bond definition.
electronegativity difference
type of bond
≥ 1.7
ionic
0.5 – 1.6
polar covalent
≤ 0.4
nonpolar covalent
exactly 007
James
It is more appropriate to describe bond character, since compounds can exhibit both ionic and
covalent properties, depending on the degree of electronegativity difference.
Practice. Determining bond type, and diagramming polar covalent bonds.
For the pairs of elements below, answer each of the following questions:
1.
2.
3.
4.
Which element of the pair would have the greatest attraction for electrons?
Would the bond be ionic, polar covalent, or nonpolar covalent?
If ionic, show the charges of the ions, and the correct formula unit.
If polar covalent, diagram the bond, showing the partial charges.
N and H
Si and Cl
Zn and O
1.
2.
1.
2.
1.
2.
Cl and O
F and Br
Al and H
1.
2.
1.
2.
1.
2.
K and S
P and H
C and F
1.
2.
1.
2.
1.
2.
H and Br
Na and I
S and O
1.
2.
1.
2.
1.
2.