Question

What is upper no. And lower no. Denoted beside an atom?

Answer 1

Explanation:

The upper one is atomic mass number (A) while the lower one beside the atom is atomic number (Z)

Answer 2

Answer:

$the \: upper \: one \: is \: atomic \: mass \: no. \: \\ < a > \: while \: lower \: one \: besides \: atom \: \\ is \: atomic \:no. \: is \: < z>$