There are 3 isotopes of hydrogen and if the average mass of all hydrogen isotopes is 1.0079 amu, which isotope is in greatest abundance in nature?

Protium

Explanation:

Isotopes -

For some elements, there are various forms possible, which have different number of neutron and same number of protons, are referred to as the isotopes.

The three isotopes possible for the element hydrogen are -

Protium, Deuterium and Tritium.

Where,

Protium has one electron, one proton and zero neutron. Deuterium has one electron, one proton and one neutron. Tritium has one electron, one proton and two neutron.

The most abundant isotope observed is Protium, with 99.98% abundance.