A neutral atom has an atomic number of 20 and a mass number of 42. How many electrons does the atom have?

The atom with 20 atomic number has 20 electrons.

Explanation:

Atomic number of an atom, Z = 20

Mass number of an atom, A = 42

Z = Atomic number = Number of proton = Number of electron (neutral atom)

Z = 20

The atom with 20 atomic number has 20 protons.

The atom with 20 atomic number has 20 electrons.

Number of neutrons = A - Z = 42 - 20 = 22

The atom with 20 atomic number has 22 neutrons.

If we have a neutral atom, then it has the same number protons and neutrons.

The number protons and neutrons for neutral atom shows atomic number.

"A neutral atom has an atomic number of 20" means that atom has 20 protons (that give charge " + 20") and 20 electrons (that give charge "-20").

Answer is 20 electrons.