Question

A neutral atom has an atomic number of 20 and a mass number of 41; how many protons, neutrons, and electrons are found within the atom?
A) 21 protons, 21 electrons, and 20 neutrons
B) 20 protons, 20 electrons, and 21 neutrons
C) 21 protons, 20 electrons, and 20 neutrons
D) 41 protons, 41 electrons, and 20 neutrons

Answer 1

•The atomic number of an atom is the number of protons it has. If the atomic number is 20 then we know the atom has 20 protons.

•The mass number of an atom is the total number of protons and neutrons the atom contains. The mass number is 41 and the number of protons is 20, just subtract 20 from 41 and you will get the number of neutrons: 41 - 20= 21. The atoms has 21 neutrons.

•The number of electrons found in an atom is equal to the number of protons. The atoms has 20 protons which means it has 20 electrons.

So, the answer is:
B) 20 protons, 20 electrons, and 21 neutrons