Question

An atom has 11 electrons and 12 neutrons. What is the number of protons

present in the atom? What is the mass number? ​

Answer 1

Explanation:

Mass number

We know that the atomic number of sodium is 11. This tells us that sodium has 11 protons and because it is neutral it has 11 electrons. The mass number of an element tells us the number of protons AND neutrons in an atom (the two particles that have a measurable mass). Sodium has a mass number of 23amu.

Answer 2

Explanation:

Example: As a sodium atom has 11 protons and 12 neutrons in its nucleus, its mass number = 11 + 12 = 23.