Choice Card

Belongs to subject Atomic Nucleus

A nucleus of hydrogen always has 1 proton, but various forms of hydrogen – called isotopes – are possible. For example, hydrogen-2 (or H-2, otherwise known as deuterium) has 1 neutron. What is the mass number A for this isotope of hydrogen?

- 3

A = N+Z = 1+1 = 2 - 2

Correct! A = N+Z = 1+1 = 2 - 0

A = N+Z = 1+1 = 2 - 1

A = N+Z = 1+1 = 2