Bohr Bury Scheme & Valence Electrons and Valency

Bohr Bury  Scheme

 

Distribution of Electrons in Various Orbits 

In 1921, Bohr and Bury gives some laws for distribution of electrons in various orbits, which are called as Bohr-Bury Scheme.

 Rules of Bohr Bury scheme are as follows-

1. Maximum number of electron in any shell should be 2n2 , where n is serial number of shell.
2. Maximum number of electron that exist in outermost shell or orbit of any atom is eight while maximum number is eighteen for penultimate shell.
3. According to this law, it is not necessary that another shell is formed after completion of 1st shell. A new shell is formed as number of electrons reaches eight in any orbit or shell.

Valence Electrons and Valency

 Outermost incomplete shell of any atom is known as Valence Shell and electron present in incomplete outermost shell are known as Valence Electrons , which participate in formation of bond.
  • If atoms have 1 to 4 valence electrons then VALENCY = Number of valence electron
  • If atoms have 5 to 8 valence electrons then VALENCY = 8 – Number of valence electron
  • But these above rule is not applicable to atoms which show variable valency
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