- Carbon is located in group 14. A carbon atom contains 6 electrons, therefore the electronic configuration is 2.4.
- It has 4 valance electrons in the outermost orbital, as shown in the diagram.
- In order to achieve a stable outer octet of electrons, it forms four covalent bonds.
When a carbon atom combines with four hydrogen atoms, it forms a molecule of methane, CH4
If two carbon atoms join, each can still combine with three hydrogen atoms to form a molecule of ethane, C2H6.
Number of Bonds
Each carbon atom is tied to other atoms through four covalent bonds. All the four covalent bonds may exist in three forms as shown below:
Carbon compounds can be divided to:
- Organic carbon compounds
- Inorganic carbon compounds
Hydrocarbons are organic compounds that contain only carbon and hydrogen.
- Hydrocarbon is a compound made out of the elements carbon and hydrogen only.
- Examples of hydrocarbon are alkane, alkene and alkyne.
- Hydrocarbons can be divided into two groups:
- saturated hydrocarbon
Saturated hydrocarbons are hydrocarbons where all its carbon atoms are tied to each other through single covalent bond only. Examples: alkanes
- unsaturated hydrocarbon
Unsaturated hydrocarbons are hydrocarbons which contain at least one double covalent bond among its carbon atoms. Examples: alkenes
- Ethanol ( C2H5OH ), ethanoic acid (CH3COOH), metal methanoate (HCOOCH3), chloromethane (CH3Cl) and others are not hydrocarbons because the molecule contains other elements such as chlorine or oxygen other than carbon and hydrogen.
- Saturated – All single bond between carbons
- Unsaturated – Has at least one double/triple bond between carbons
Comparing Saturated and Unsaturated Hydrocarbon
|Saturated Hydrocarbon||Unsaturated Hydrocarbon|
|Combustion||Produce less soot||Produce more soot|
|Reaction with bromine water||The brown colour of bromine remain unchanged||Decolourise the brown colour of bromine|
|Reaction with potassium manganate(VII) solution||The purple colour of potassium manganate (VII) solution remain unchanged||Decolourise the purple colour of potassium manganate (VII) solution|
Sources of Hydrocarbon:
- Natural gas
Combustion of Hydrocarbon
- Complete combustion – organic compounds burn completely which form CO2 and H2O
- Incomplete combustion– organic compounds burn with limited supply of O2 which form C (soot), CO, CO2 and H2O.
- The soot from the combustion of a hydrocarbon depends on the percentage of carbon it contains.
- Higher carbon percentage in the hydrocarbon molecule will result sootier flame.
- A series of compounds with similar chemical properties, in which members differ from one another by the possession of an additional CH2 group, is called a homologous series.
- Each homologous series must have the following four characteristics:
- Every member in the homologous series can be represented by a common formula. For example:
- Alkane: CnH2n+2
- Alkene: CnH2n
- Alcohol: CnH2n+1OH
- Carboxylic acid : CnH2n+1COOH
- Ester: CnH2n+1COOCmH2m+1
- Every member differ from others by the group -CH2– which has the relative mass 14. For example:
- Members of the same homologous series can be prepared through one common method. For examples, All alkenes can be prepared by dehydration of relevant alcohols.
- Members of the homologous series have the same chemical properties. For example:All alkenes show addition reaction as added into bromine.
- Members of the same homologous series have the same chemical properties because of the presence of a common functional group in all the molecules of the series.
- Functional group is a group of atoms tied together which will take part in a chemical reaction therefore determine the chemical properties of the series.
- Therefore, the homologous series is a family of organic compound that is made out of members with common functional group, common chemical properties, and consecutive members are differ by one carbon atom and two hydrogen atom, namely, –CH2-.
- Table below shows some homologous series and their respective general formula and functional group.
|Carbon Compounds||General Formula||Functional group|
|Alkane||CnH2n+2||Carbon-carbon single bond – C – C –|
|Alkene||CnH2n||Carbon-carbon double bond – C = C –|
|Alcohol||CnH2n+1OH||Hydroxyl group – OH|
|Carboxylic Acids||CnH2n+1COOH||Carboxyl group – COOH|
|Esters||CnH2n+1COOCmH2m+1||Carboxylate group – COO –|