Question

In the symbol (4/2)He, the superscript 4 is the ? for helium, and the subscript 2 is the ? for helium.

Answer 1

superscript 4 is the atomic mass of helium
subscript 2 is the proton (atomic) number of helium

hope that helps :)

Answer 2

A = 4 is the mass number of this nucleus
Z = 2 is the atomic number

Answer 3

\(^A_Z\text{X}\) is an atom X with A nucleons and Z protons

\(^4_2\text{He}\) is an atom with 4 nucleons and 2 protons