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

a.) a negative charge
b.) a positive charge
c.) a mass number of 38
d.) an atomic number of 20

an atom that has 18 protons, 18 neutrons and 20 neutrons. This atom has mass number of 38

mass number is calculated as number of protons + number on neutrons

therefore the mass number of the atom = 18+20= 38

Since the atom has a electronic configuration of 2.8.8,the atom cannot be negatively or positively charged because it is stable.

The atomic number of the atom is 18 since atomic number is equal to number of protons

okay yes , aha.

it's c. elements are placed in rows based on how may valencies electrons have.