The Absorption & Emission of EM Radiation

Introduction

• Electrons in an atom are arranged in energy levels
  • Lower energy levels are closer to the nucleus, whilst higher energy levels are further away from the nucleus of the atom
• These electrons can absorb energy
• This happens when waves of electromagnetic radiation (such as light and heat) hit them
• When electrons absorb electromagnetic radiation, they move to a higher energy level
  
  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 unstable
• 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

Tips 

Whilst you are expected to know about energy levels and the absorption and emission of electromagnetic waves, you are not expected to know about the number of electrons in each energy level or the way in which they fill up - that's all part of Chemistry.