What measures the number of protons and neutrons in an atom? -Atomic Number
-Atomic Mass
-Isotopes
-Olons

atomic mass

Explanation:

Mass Number. The mass number (A) of an atom is the total number of protons and neutrons in its nucleus. The mass of the atom is a unit called the atomic mass unit (amu).

answer; i believe the correct answer is (c) /// is a homogeneous mixture of gaseous substance nitrogen,oxygen and smaller amounts of other substancesmixtures can be either ( homogeneous or heterogeneous)plz check first good luck