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Isotopes 2

Chemistry: Edexcel IGCSE, topic 3.1.7

Electronic Structure

Electrons have fixed positions in atoms called shells or energy levels. These shells (or energy levels) go around the atom's nucleus.

Filling electron shells

Filling electron shells

  • Electrons fill an atom's shells in order of increasing energy.
  • The closer a shell is to the nucleus, the lower its energy level, so the first shell that is filled is the closest to the nucleus.
Electron configuration

Electron configuration

  • Electron configuration tells us how an atom's electrons are organised.
  • The inner shell (closest to the nucleus) can have a maximum of 2 electrons and the next two shells can have a maximum of 8 electrons.
  • Any extra electrons are then put into a fourth shell.

Test yourself on Isotopes 2

  • How many shells contain electrons in an atom with the electronic structure 2,8,8,1?

  • How many shells contain electrons in an atom with the electronic structure 2,8?

  • What is the electronic structure of this atom?

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