The structure of an atom

• Atoms are very small, having a radius of about 1 x 10^-10 m
• The basic structure of an atom is a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons
• The radius of a nucleus is less than 1/10000 of the radius of an atom. Most of the mass of an atom is concentrated in the nucleus
• • The electrons are arranged at different distances from the nucleus (different energy levels)
• The electron arrangements may change with the:

  • absorption of electromagnetic radiation (electron would move further from the nucleus; a higher energy level)
  • emission of electromagnetic radiation (electron would move closer to the nucleus; a lower energy level)