Chapter 4 - Atomic Structure - 4.3 Distinguishing Among Atoms - 4.3 Lesson Check - Page 119: 30

Atomic number represents the number of protons in the nucleus of an atom and distinguishes an atom of an element from other elements. Atomic mass is the sum of both protons and neutrons in the nucleus of an atom in an element.

Atomic number represents the number of protons in the nucleus of an atom and distinguishes an atom of an element from other elements. Atomic mass is the sum of both protons and neutrons in the nucleus of an atom in an element. They are different because atomic number only accounts for the protons however atomic mass accounts for both protons and neutrons.