EVERYDAY SCIENCE

Detailed explanation-1: -The mass number of the atom (M) is equal to the sum of the number of protons and neutrons in the nucleus. The number of neutrons is equal to the difference between the mass number of the atom (M) and the atomic number (Z).

Detailed explanation-2: -Protons and neutrons have approximately the same mass, about 1.67 × 10-24 grams, which scientists define as one atomic mass unit (amu) or one Dalton.

Detailed explanation-3: -Both protons and neutrons have a mass of 1, while electrons have almost no mass.

Detailed explanation-4: -The total number of protons and neutrons in the nucleus of an atom is called its mass number.

Detailed explanation-5: -The mass number tells us the nucleus contains 19 particles in total. Since 9 of these are protons, the other 10 are neutrons. We call it the mass number because virtually all the mass in an atom comes from the protons and neutrons-electrons weigh about 1/2000th of the mass of a proton or neutron.