What is catenation property of carbon?
Catenation property is found in organic as well as in inorganic compounds. The catenation property mainly shows carbon element in organic chemistry.
When two or more atoms of an element combine with each other through the covalently single bond, double bond or triple bond to form a long chain structure, then that characteristic of the elements is called catenation property.
When a large number of carbon atoms are covalently bonded with each other through the single bond, double bond or triple bond, resulting in the formation of a large number of cyclic or open chain compounds, so in the case of carbon this properties is called catenation property of carbon.
Why Does Carbon Shows Highest Degree Of Catenation?
The ionization potential of carbon is quite high and its electron affinity is of moderate quality. The sizeof carbon atom is small.
Now, it has been experimentally found that the carbon atom shows highest degree of catenation. Observations have shown that there are three main reasons for showing of catenation property by carbon atom.
(I)The C — C bond energy is higher than their expected value due to small size of carbon atom.
(II)Carbon shows tetravalency and forms large number of covalent bonds.
(III)Carbon occupied less diffused atomic orbital due to small atomic size and hence a strong overlapping occurs among the orbitals.
What is the importance of catenation property of carbon?
A large number of carbon atoms easily form covalent bonds with each other to form long chain structures. This property of carbon is called catenation property.
It is a very important property of carbon atom. This is because the number of organic compounds in nature is so high because of this catenation of carbon.
Catenation of property decreases down the group
In general, the catenation property of the elements decreases as we move from top to bottom along a group in periodic table.
But exception of catenation property is seen in the case of group-15 and group-16 elements of the periodic table.
For example, in case of group-15 elements, the catenation property of P- atom is higher than that of N- atom which is reverse of actual order.
This is due date higher bond strength of P-P bond as compared to N-N bond. The weakness of N-N bond is due to repulsion between the lone pairs present on the two nitrogen atoms. But N2 molecule is stable due to triple bond.
Phosphorus atom is also contains lone pairs but due to longer bond length, the lone pairs exert less repulsion. Also the vacant d-orbitals on phosphorus involved in lone pair delocalization.
The catenation property of sulphur atom is also higher than that of oxygen atom due to above similar reason.
Why sulphur shows more catenation property than oxygen?
The bond energy of O — O double bond is thrice the O — O single bond energy. Whereas S=S bond energy is less than twice the S-S bond energy.
So S prefers forming two single bonds over one double bond, so chain continues. In case of oxygen formation of double bond is preferred, however catenation to small extent can be observed. For example peroxides, ozone.
Why does carbon show more catenation than silicon?
Both carbon and silicon atoms show maximum catenation property in their pure elemental forms under similar and ideal conditions.
But the catenation property found in carbon atom is much higher than silicon atom for several reasons.
Carbon can form stable π bonds but silicon can’t. Carbon-carbon single bonds are around 80% stronger than silicon-silicon bonds, making catenated carbon more stable than catenated silicon.
Oxygen is the third most common element in the universe. Catenated carbon is pretty stable even in the presence of oxygen, because C-C bonds are about 85–90% as strong as C-O bonds.
On the other hand, Si-Si bonds are only about 32–35% as strong as Si-O bond which are actually stronger than C-O bonds.
For the above reasons, it has been found that a large number of carbon-carbon chains of any length can be formed and they will be pretty stable. But silicon chains can’t grow past around eight silicon atoms in length.