Question

What is an isotope? list the isotopes of hydrogen in order from lighter to heavier. which is the most common among them?

Answer 1

Isotopes= a group of atoms with the same no. of protons , but different no. of neutrons

Hydrogen isotopes

$^1H\implies ^2H\implies ^3H$

The name of the second isotope is deuterium and the name of the third isotope is tritium(radioactive).The most abundant isotope is $^1H$