What is valency and explain the failures of octave rule of filling valency.
Answers
Valency- It it is the combining capacity of an element.
=> For s-Block and p-block outermost sell (n s,np) are known as valence shell.
=> For d- block n s and (n -1)d electron is known as valence electron.
Failures of octave rule -
There are mainly four reasons for failure
1. Incomplete octet or Electron deficient- Those species in which central atom has less than 8 electron in their outermost shell.
Examples- BF3, BCl3 ,BBr3 etc.
2. Expansion of octet or Electron efficient- Those species in which central atom has more than 8 electron in their outermost shell.
Examples- PCl5 , SF6 , IF7 etc.
3. Pseudo Inert gas configuration- Cations which have 18 electron in their outermost shell is known as pseudo inert gas configuration.
Examples- Zn^+2 , Cd^+2 , Cu^+ etc.
4. Odd Electron species- Those species in which central atom have odd number of electron in their outermost shell.
Examples- No, NO2 ,ClO2 etc.