1.The general formula/molecular formular of a compound is the number of each atoms of elements making the compound e.g.

Decane has a general/molecular formula C10H22 ;this means there are 10 carbon atoms and 22 hydrogen atoms in a molecule of decane.

2.The structural formula is the arrangement / bonding of atoms of each element making the compound e.g

Decane has the structural formula as in the table above ;this means the 1st carbon from left to right is bonded to three hydrogen atoms and one carbon atom.

The 2nd carbon atom is joined/bonded to two other carbon atoms and two Hydrogen atoms. e.t.c

3.Since carbon is tetravalent ,each atom of carbon in the alkane MUST always be bonded using four covalent bond /four shared pairs of electrons.

 4.Since Hydrogen is monovalent ,each atom of hydrogen in the alkane MUST always be bonded using one covalent bond/one shared pair of electrons.

5.One member of the alkane differ from the next/previous by a -CH2 -  group.

 e.g

Propane differ from ethane by one carbon and two Hydrogen atoms form ethane. Ethane differ from methane also by one carbon and two Hydrogen atoms

6.A group of compounds that differ by a -CH2 -  group from the next /previous consecutively is called a homologous series.

7.A homologous series:

(i)differ by a CH2  group from the next /previous consecutively

(ii)have similar chemical properties

(iii)have similar chemical formula that can be represented by a general  formula e.g

 alkanes have the general formula CnH2n+2.

(iv)the physical properties (e.g.melting/boiling points)show steady gradual change)

8.The 1st four alkanes have the prefix meth_,eth_,prop_ and but_ to represent 1,2,3 and 4 carbons in the compound. All other use the numeral prefix pent_,Hex_,hept_ , etc to show also the number of carbon atoms.

9.If one hydrogen atom in an alkane is removed, an alkyl group is formed.e.g

draw structural formulae of alkanes with branched chains and name them