Question

What would happen to an atom if it did not have neutrons ?

Answer 1

well the neutrons will be protons.

Answer 2

Neutrons provide stability to the nucleus of the atom. This is why virtually all isotopes of all elements have a number of neutrons in their nucleus.

Protons by themselves do not at all like getting together: their positive charges repel. A nuclear force overcomes that repulsion to keep together and it works best with neutrons to help bind the protons.

If an atom somehow lost its neutrons, the nucleus would become unstable at decay into something else.

You might enjoy this (clunky) web page:
http://www.igcar.gov.in/nuclear/atomic_nucleus.htm