Class 9 Chemistry Structure of The Atom Valence Electrons

Valence Electrons

  • The electrons present in the outermost shell of an atom are known as valence electrons (or valency electrons) because they decide the valency (combining capacity) of the atom.
    • For Example: - The atomic number of sodium is 11, which means sodium atom has 11 electrons in it.
    • So the electronic configuration K (2), L (8), M (1).
    • In the sodium atom, M shell is the outermost shell or valence shell.
    • There is 1 electron in the outermost shell of sodium atom; therefore, sodium atom has 1 valence electron.
  • Those electrons of an atom which take part in chemical reactions are called valence electrons.
  • Valence electrons are located in the outermost shell of an atom.
  • Note:-
  • In order to find out the number of valence electrons in an atom of the element, we should write down the electronic configuration of the element by using its atomic number.
  • The outermost shell will be the valence shell and the number of electrons present in it will give us the number of valence electrons.
  • Valency of a metal = No. of valence electrons in the atom
  • Valency of a non-metal = (8 – No. of valence electrons in its atom)

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