Question

The atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. What are its atomic number and mass number ?

Answer 1

Atomic number refers to the number of protons in an atom. An atom with 4 protons (beryllium) would have an atomic number of 4.

Atomic mass is the sum of the number of protons and neutrons in an atom. An atom with 4 protons and 5 neutrons would have an atomic mass of 9.

Electrons do not factor in to atomic number nor atomic mass