A model of an atom which contains 24 electrons, 25 protons and 26 neutrons has some of its particles inside a nucleus at the centre of the model. What is the nucleon number (mass number) of the atom?

The nucleon number of given atom = 51

Explanation:

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.

The mass number is also called nucleon number.

The nucleon number of given atom = number of protons + number of neutrons

The nucleon number of given atom = 25 + 26

The nucleon number of given atom = 51

thats how its supposed to be