Atom: GCSE Chemistry Definition

What is an atom?

In GCSE chemistry, atoms are the building blocks of all matter. They are the smallest part of an element that can exist.  Atoms consist of protons, neutrons and electrons. Protons and neutrons are located in the nucleus of an atom, and electrons orbit the nucleus in shells.

You can use the Periodic Table to deduce the number of protons, neutrons and electrons in an atom: 

• The atomic number is the number of protons

• In an atom, the number of electrons is equal to the number of protons 

• The mass number is the number of protons and neutrons, so the number of neutrons can be deduced by taking the atomic number away from the mass number. 

For example, the atomic and mass number for beryllium are shown here:

• It has an atomic number of 4 = 4 protons. 

• The number of electrons are equal to the number of protons = 4 electrons. 

• The number of neutrons = mass number - atomic number, so 9 - 4 = 5 neutrons

Atom Revision Resources to Ace Your Exams

Save My Exams offers GCSE resources to help you master the atom and boost your grades. The atomic structure revision notes simplify concepts, while topic questions let you practice exam-style questions to sharpen your skills. Use the flashcards on the model of the atom to quickly test your knowledge of key terms, helping you retain information and feel more confident for exams

Explore Our GCSE Chemistry Revision Resources