British Sign Language Glossaries of Curriculum Terms

BSL Chemistry Glossary - mass number - Definition

Mass Number and Atomic Number.

On the board we have a drawing/representation of an atom. In the outer ring circling we have Electrons and in the centre is the Nucleus which is made up of Neutrons and Protons.

Atoms come in a range of sizes and this is just one example - Helium. The chemical symbol for Helium is He. If we look at the Periodic Table we can see all the different elements and these have numbers added to them like this - ⁴₂ He

What these numbers refer to are the Mass Number, which in Helium is ⁴ and the Atomic Number is ₂ We can work the Mass Number of an atom by adding the number of Neutrons and Protons which in this example = 4 (2 Protons and 2 Neutrons). The Atomic Number equals the number of Protons which in this case is 2.

To recap, the Mass Number is the sum of the number of Protons and Neutrons; the Atomic Number is the number of Protons the atom has.