An atom has 18 protons, 18 electrons, and 20 neutrons.

This atom has?

a negative charge

an atomic number of 20

a mass number of 38

a positive charge

a mass number of 38

Explanation:

X This atom has no a negative charge.

because, number of protons (18) & electrons (18) are same. so, This atom is neutral.

X This atom has an atomic number of 20.

Because, it has 18 protons. so, This atom has an atomic number of 18.

X This atom has a positive charge

because, number of protons (18) & electrons (18) are same. so, This atom is neutral.

mass number of 38

Explanation:

Charge is 0 - No. of protons is equal to nom. of electrons, so no charge

Atomic number is 18 - Atomic number is number of protons

Mass number is 38 - mass number is number of protons AND neutrons