Question

The reason for the existence of isotopes is change in
a. atomic number
b. electron number
c. neutron number
d. proton number

Answer 1

Isotopes are same elements with different masses.A nucleus with all protons will not be stable and hence will repel each other

Answer 2

Answer:

The reason for the existence of isotopes is a change in (c) neutron number.

A given element can have different isotopes owing to the difference in the number of neutrons but the number of protons and electrons remains the same.

The various isotopes of an element have a different mass number( number of protons+number of neutrons). In the case of radioactive isotopes, one isotope is found to decay over time in order to give rise to another isotope.