Electron Structure (Edexcel GCSE Physics: Combined Science)

• Electrons in an atom orbit around the nucleus at particular distances, known as energy levels
• A certain number of electrons can occupy each energy level
  • For example, only two electrons can orbit in the first energy level
  • Only eight electrons can fit in the second energy level, and eight in the third as well

• The higher the energy level, the further the distance of the electron from the nucleus

In this diagram the first two energy levels are full. Electrons further from the nucleus have more energy

• Like moving up a ladder, electrons in higher energy levels have greater potential energy because they have more distance between them and the nucleus

Absorption of Electromagnetic Radiation

• Electrons are able to temporarily move between energy levels when they absorb or emit energy
  • This means that they change their orbit

• When electrons absorb electromagnetic radiation, they move to a higher energy level
  • This happens when waves of electromagnetic radiation (such as light and heat) hit them

The electron absorbs electromagnetic radiation which causes it to move up an energy level

• Dark coloured objects are good absorbers of radiation
  • They appear dark because they do not reflect the energy that hits them

Emission of Electromagnetic Radiation

• When an electron has moved up an energy level, it will be in an excited state
• Eventually, it will move back down to its original energy level, which will be closer to the nucleus
  • As it moves back down, it emits a wave of electromagnetic radiation

The electron emits a wave of electromagnetic radiation and moves down an energy level

• All of the colours in the visible spectrum are produced in this way
• The light waves come from electrons moving down energy levels and emitting electromagnetic radiation