Here are the essential concepts you must grasp in order to answer the question correctly.
Isotopes
Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons. This results in different atomic masses for the isotopes. For example, hydrogen has three isotopes: protium (1H), deuterium (2H), and tritium (3H), each differing in neutron count.
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Molecular Composition
The molecular composition of a compound is determined by the types and numbers of atoms it contains. In the case of HCl, the molecule consists of one hydrogen atom and one chlorine atom. The isotopes of hydrogen will combine with the isotopes of chlorine to form different isotopic versions of HCl.
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Subatomic Particles
Atoms are composed of protons, neutrons, and electrons. Protons are positively charged and found in the nucleus, neutrons are neutral and also in the nucleus, while electrons are negatively charged and orbit the nucleus. The number of these particles varies with isotopes, affecting the atomic mass but not the chemical behavior.
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