A molecule of oxygen, O2, can be
represented in different ways to show the double covalent bond present between the
two oxygen atoms. Which of the following formulas
correctly shows a molecule of oxygen? We have been given a list of
options from (A) to (E).
To understand the bonding in
oxygen, let’s first find oxygen in the periodic table. The proton number or atomic number
is eight. This is equivalent to the number of
protons, and in a neutral atom, the number of electrons. Two electrons fill the first
shell. The remaining six electrons fill
the second shell.
The question tells us that there
are two atoms of oxygen in an oxygen molecule. We can represent these two atoms
with dot-and-cross diagrams. In this diagram, the electrons in
one oxygen atom are represented by dots and the electrons in the other oxygen atom
are represented by crosses.
Before we understand how the atoms
combine, we need to recall the octet rule. The octet rule states that atoms
tend to create chemical bonds to have eight valence shell electrons and the same
electron configuration as the nearest noble gas.
Both atoms currently have six
outer-shell electrons. And they should have eight once
bonded. To allow each atom to have eight
electrons in its outer shell, oxygen forms a double covalent bond, as stated in the
question, where covalent bonds are chemical bonds that are formed when two nonmetal
atoms share one or more pairs of electrons. A single covalent bond is formed of
a single electron pair, whereas a double covalent bond is formed of two electron
pairs. This is the type of bond in an
The dot-and-cross diagram allows us
to see that each atom donates two electrons to form this double bond. This diagram depicts the double
covalent bond present between two oxygen atoms. But we can represent it in another
way. Each bond formed from two electrons
can be represented by a solid line between the two oxygen atoms. Since oxygen has a double covalent
bond formed of four shared electrons, it can be represented by two solid lines. Thus, the formula which correctly
shows a molecule of oxygen can be found in answer choice (A).