OCR Gateway GCSE Chemistry

Revision Notes

1.2.2 Atomic Structure

Test Yourself

Atomic Structure

  • All substances are made of tiny particles of matter called atoms which are the building blocks of all matter
  • Each atom is made of subatomic particles called protons, neutrons, and electrons
  • The protons and neutrons are located at the centre of the atom, which is called the nucleus
  • The electrons move very fast around the nucleus in orbital paths called shells
  • The mass of the electron is negligible, hence the mass of an atom is contained within the nucleus where the protons and neutrons are located

Carbon atom structure, IGCSE & GCSE, AS & A Level Chemistry revision notes

 The structure of the Carbon atom

Exam Tip

The atom is the smallest part of an element that exists even though it can be divided into smaller particles. The atom is the smallest part as it retains the properties of the element while the subatomic particles do not.

The Size of Atoms & Molecules

  • Atoms are extremely small with a radius of about 1 x 10-10 metres
  • The central nucleus contains protons and neutrons only which are packed close together in a small region of space
  • The radius of the nucleus is about 10 000 times smaller than that of the atom, so it is an extremely small region of space compared to the overall size of the atom
  • This means that rather than being evenly spread out throughout the atom, virtually all of the atom's mass is concentrated inside the nucleus
  • Electrons have a much smaller mass than protons and neutrons (1 proton has the same mass of around 1840 electrons) and move in the space outside the nucleus in orbits
1-2-2-size-of-atomsAtoms are unimaginably tiny!

Subatomic Particles

  • Elements are made of tiny particles of matter called atoms
  • Each atom is made of subatomic particles called protons, neutrons and electrons
  • These subatomic particles are so small that it is not practical to measure their masses and charges using conventional units (such as grams or coulombs)
  • Instead, their masses and charges are compared to each other, and so are called ‘relative atomic masses’ and ‘relative atomic charges’
  • These are not actual charges and masses, but rather charges and masses of particles relative to each other
  • Protons and neutrons have a very similar mass, so each is assigned a relative mass of 1
  • Electrons are 1836 times smaller than a proton and neutron, and so their mass is often described as being negligible
  • The relative mass and charge of the subatomic particles are:

Relative Mass & Charge of Subatomic Particles Table

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.