What is a carbonyl group? Provide the different homologous series of carbonyl compounds.

(N/A) Organic compounds containing a carbon-oxygen double bond $(C=O)$ are called carbonyl compounds. The carbon atom of the carbonyl group is $sp^2$ hybridized and forms three sigma bonds. The homologous series of carbonyl compounds are as follows:

Name of homologous series	Common formula	Functional group
$(i)$ Aldehydes	$R-CHO$	$-CHO$
$(ii)$ Ketones	$R-CO-R'$	$>C=O$
$(iii)$ Carboxylic acids	$R-COOH$	$-COOH$
$(iv)$ Esters	$R-COOR'$	$-COOR'$
$(v)$ Acid halides	$R-COX$	$-COX$
$(vi)$ Amides	$R-CONH_2$	$-CONH_2$