Question

1. the ________________________ of an element is the total number of protons and neutrons the ______________________________ of the atom.

Explanation:

In chemistry (a subfield of Natural Science), the mass number of an element is defined as the total number of protons and neutrons in the nucleus of the atom. So we need to fill in "mass number" for the first blank and "nucleus" for the second blank.

Answer:

The first blank: mass number; The second blank: nucleus