how do we know that an element has a vacant d-orbital??

Asked by Sunil Soni | 13th Aug, 2015, 01:43: PM

Expert Answer:

Covalency of an element for example hydrogen, nitrogen, oxygen, fluorine is the total number of unpaired electrons in s or p orbitals.

Hydrogen for example (H®1s1) has only one unpaired electron and shows a covalency of one.

N atom (N→2s22px12py12pz1) has three unpaired electrons and shows a covalency of three.

O atom (O→2s22px22py12pz1) has two unpaired electrons and shows a covalency of two.

F atom (F→2s22px22py22pz1) has one unpaired electrons and shows a covalency of one.

If you observe these elements given above have only s and p orbitals in their valence shells and do not contain vacant d orbitals.

However elements like P, S, and Cl contain vacant d-orbitals and show different values of covalency in different covalent compounds.

It is called variable covalency and is due to the presence of vacant d-orbitals in the valency shell of these elements.

Some examples of elements showing different covalencies in compounds.

Elements

Different covalencies

Examples of Compounds

Halogens(Other than fluorine)

1

3

5

7

ICl

ICl3

ICl5

ICl7

Sulphur

2

4

6

SCl2

SF4

SF6

Phosphorus

3

5

PCl3

PCl5

 

Variable covalency of phosphorus of P atom (3,5)

P in Ground state : 3s2 3px1 3py1 3pz1

 

 

Phosphorus in its excited state: 3s1 3px1 3py1 3pz13d1

 

Answered by Vaibhav Chavan | 14th Aug, 2015, 08:36: AM