N atom contains 70 protons, 70 electrons, and 99 neutrons. what is the mass number?

Answer is. mass number of atom N is 169.

e⁻ = 70; number of electrons.

p⁺ = 70, number of protons.

n° = 99; number of neutrons.

A = ?, mass number or atomic mass.

The mass number A is sum of the number of protons and the number of neutrons in atom.

A = n° + p⁺.

A = 99 + 70.

A = 169.