Learn: Atomic Structure

Welcome!Today we'll explore atomic structure. This is a key concept in Edexcel GCSE Chemistry, and understanding it will help you build a strong foundation for other topics!

What is an atom?An atom is the smallest unit of matter which cannot be broken down further without losing its properties. It consists of three main subatomic particles: protons, neutrons, and electrons.

The structure of an atomAtoms have a nucleus at the centre, which contains protons and neutrons. The electrons orbit around the nucleus in energy levels, also known as shells. Most of the mass of an atom is concentrated in the nucleus, while the electrons are much smaller and move around it.

What are protons, neutrons, and electrons?Protons are positively charged particles located in the nucleus. Neutrons are neutral particles, also found in the nucleus. Electrons are negatively charged particles that move around the nucleus in energy levels.

Atomic number and mass numberThe atomic number is the number of protons in an atom. It uniquely identifies the element. The mass number is the sum of protons and neutrons in the nucleus, which tells you the total mass of the atom.

How are electrons arranged?Electrons are arranged in energy levels or shells around the nucleus. The first shell can hold up to 2 electrons, the second can hold up to 8, and the third can hold up to 8 as well. This arrangement is called the electron configuration.

Review Time!Well done! You've learned about the structure of atoms, subatomic particles, and electron arrangements. Let's test your understanding with some review questions.