Electronic Configuration

Arrangement of Electrons

• The electronic configuration of an atom refers to the way in which electrons are arranged on an atom. Electrons are found on the shells of atoms.

• Each shell possesses a limit on the number of electrons it can hold. Elements which have atomic numbers of 1-20 have the following limits:

  • The first shell has a maximum of 2 electrons.
  • The second shell has a maximum of 8 electrons.
  • The third shell has a maximum of 8 electrons.
  • The fourth shell has a maximum of 18 electrons.

• The electron configuration of an atom is written in the order of its shells.

  • For example, the electronic configuration for Calcium (Ca) is represented as 2,8,8,2. This is due to Calcium's atomic number being 20.

    ![]( "Diagram of a Calcium Atom")

    1-20

    

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    What is this?

    This is a numerical representation of the electrons in an atom, it is written according to the number of electrons in each shell

    Example:

    • K→19 = 2, 8, 8, 1