Page 59 - Chemistry_Form_2

Chemistry
for Secondary Schools

Two electrons are
shared to form one
covalent bond

FOR ONLINE READING ONLY

Or
H – H or H 2
Figure 3.4: Covalent bonding in a hydrogen molecule

Note: A single line between two atoms indicates a single covalent bond carrying
an electron pair. Two lines are used to represent bonding of two pairs,
three lines represent three pairs, and so on.

Oxygen requires two electrons to acquire the stable atomic structure. Thus, two
atoms of oxygen combine and share four electrons between them (Figure 3.5).

Two pairs of electrons
are shared to form
double covalent bond

Oxygen atom Oxygen atom Oxygen molecule
Or, considering only the outermost shells:

O = O or O
2

Figure 3.5: Double covalent bond in oxygen molecule
Covalent bonding also occurs between atoms of different elements such as
between hydrogen and chlorine. Hydrogen requires one electron to attain a
stable helium electronic configuration, while chlorine requires one electron to
acquire the argon electronic configuration. The two atoms combine by sharing
two electrons between them (Figure 3.6).

52 Student’s Book Form Two

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