How do you calculate the atomic number and mass number of an atom?

Answer 1

Atomic number tells how many protons are inside an atom's nucleus and therefore also how many electrons the atom has.

An atom's mass number is the number of protons AND neutrons in the atom's nucleus and this will vary for each isotope of an element.

Answer 2

The mass number is the sum of the number of neutrons and the number of protons. Since the atomic number is the same as the number of protons, you can also say that the mass number is the sum of the atomic number and the number of neutrons.
The atomic number denotes how many protons there are in the atom, mass number - atomic number gives the number of neutrons in an atom.

If the atomic number of an element is 7, this means there are 7 protons and 7 electrons

Answer 3

Atomic Number is equal to the number of Protons. Atomic Mass Number is equal to the number of nucleons (nucleon is a Proton or Neutron). So to get the number of Neutrons, subtract the atomic number from the atomic mass number.

If the atom is electrically neutral (no charge), then the number of electrons will equal the number of protons.

Answer 4

Except for hydrogen-1 and helium-3, the mass is always at least twice as much as the number. The ratio between the mass and the number increases with increasing atomic number, but as far as I know never exceeds 2.5.

Answer 5

This is a nuclear decay equation. There are links below to a couple examples in related questions.

Answer 6

atomic number is the number of either protons or electrons and mass number is the total number of proton and neutrons in the atom