Question

The molecular formula of heavy water is:
a.) $$D_{3}O$$
b.) $$D_{2}O$$
c.) $$DO$$
d.) $$D{O}_2$$

Answer 1

Hint: The formula of heavy water is the same as that of normal water. This is because oxygen has six valence electrons and can covalently bond as long as its valency is satisfied. Deuterium is an isotope of hydrogen.

Complete step by step answer:
Deuterium (D) is an isotope of hydrogen. It is present in very low quantities in the environment. It is around 0.0156 percent of the total environmental oxygen. It contains one neutron and one proton. It is called ‘deuterium’ because it has double the mass of protium, it weighs around 2.014 u. For the same reason, it is also known as heavy hydrogen.
And therefore, water made by deuterium is known as heavy water. It is the same as normal water, the difference being, its mass is 10 percent more than normal water.
Water is a covalent compound, formed by sharing of electrons between oxygen and two hydrogen (deuterium) atoms. Oxygen, having 6 electrons in its valence, forms two bonds with deuterium. Therefore, the formula of heavy water is $$D_{2}O$$. The structure can be represented as –

Therefore, the answer is – option (b) – The molecular formula of heavy water is $$D_{2}O$$.

Additional Information:
There are seven isotopes of hydrogen, i.e. Hydrogen-1 (protium), Hydrogen-2 (deuterium), Hydrogen-3 (tritium), Hydrogen-4, Hydrogen-5, Hydrogen-6, Hydrogen-7.

Note: The other two main isotopes of hydrogen are – protium and tritium.
Protium – It is the hydrogen which occurs in the periodic table. It is also known as atomic hydrogen. It contains one neutron and one proton. It is very stable. 99.9 percent of hydrogen present in the environment is protium.
Tritium – This isotope of hydrogen contains two neutrons and one proton. It is quite unstable, with a half-life of 12.32 years.