Question

Explain why atoms have different isotopes. In other words is it that? Helium com exists in three different forms.

Answer 1

The number of Protons, massive positively charged nuclear particles defines the identity of nucleolus. Isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.

Complete step by step answer:
Isotopes- The nucleus may contain various no. of neutrons, massive, neutrally charged nuclear particles which gives to the existence of isotopes.
For hydrogen, $z=1$, that is there is a proton in all hydrogen nuclei. Some hydrogen nuclei contain $1$ neutron to give the deuterium isotope, ${{2}_{H}}$ an even smaller number of hydrogen nuclei contain $2$ neutrons to give the tritium isotope ${{3}_{H}}$ most atoms have a number of isotopes in different propositions. In this question we explain that helium exists in three different forms, the helium atom has $z=2$ there are $2$ nuclear protons. The most common isotope of helium is ${{4}_{He}}{{.3}_{He}}$ and ${{5}_{He}}$ are small abundances.

So, the correct answer is Option C.

Note: Different isotopes of some element have the same atomic number. They have the same number of protons. The atomic no. is decided by the number of protons.