Question

What does the bottom number within each box of the periodic table refer to? How can it be used to determine the number of neutrons inside an element?

Answer 1

Atomic mass
It refers to how many protons and neutrons there are in an element

Answer 2

Atomic Number

Step-by-step explanation:

The number below the symbol is the atomic number and this reflects the number of protons in the nucleus of each element's atom. Every element has a unique atomic number.