In the previous section, we saw the different allotropes of carbon. In this section we will learn about the isotopes of carbon.
■ Isotopes are atoms of the same element, having same atomic number Z, but different mass number A
• They will have the same Z because, the number of protons in all those atoms will be the same
• They have different mass numbers because, the number of neutrons will be different.
• We saw the details earlier here.
■ Carbon-12, carbon-13 and carbon-14 are the different isotopes of carbon.
• 99% of the carbon that occurs in nature is in the form of carbon-12
♦ The mass of carbon-12 atom is taken as the reference for expressing the atomic masses of other elements. We saw details here.
• Carbon-14 is a radioactive isotope. The presence of this isotope in a material can be used to determine the age of that material. This method of determining age is called carbon dating.
Compounds of Carbon
• Earlier in this chapter, we saw hydrocarbons. They are compounds of carbon which are formed when carbon combines with hydrogen
• Now we will see those compounds which are formed when carbon combines with some other elements
Carbon dioxide
• Carbon dioxide is a gas present in the atmosphere. It is produced mainly by the combustion of fuels.
■ How is carbon dioxide produced when combustion of fuels takes place?
• The fuels contain carbon or 'compounds of carbon'
• When the fuels burn, this carbon or ‘compounds of carbon’ reacts with oxygen. This reaction produces carbon dioxide. Let us see the equations:
• Reaction of carbon with oxygen:
C + O2 → CO2
• Reaction of a 'compound of carbon' with oxygen:
CH4 + 2O2 → CO2 + 2H2O
• During photosynthesis, plants take in carbon dioxide from the atmosphere.
• They use it to prepare food. Thus the carbon becomes part of the plant body.
• These plants are eaten by animals. Then the carbon becomes part of the animal body.
• When the animals respire, they take in oxygen. The carbon in their body is given out as carbon dioxide.
• Thus the carbon dioxide enters back into the atmosphere.
Another way:
• When the plants and animals decay, they are converted into coal and petroleum. These are fossil fuels.
• When these fossil fuels are burnt, carbon dioxide is produced. In this way also, the carbon dioxide enters back into the atmosphere.
• Used to make soda water and soft drinks
• Used in the manufacture of washing soda and baking soda
• Used in the manufacture of chemical fertilisers like urea
• Used in carbogen (95% oxygen and 5 % carbon dioxide) used for artificial respiration
• The solid form of carbon dioxide is called dry ice. It is used as a refrigerant and also to create stage effects resembling clouds
• The infra red rays are thermal radiations. They are referred to as heat waves also. Because they tend to increase the temperature of substances upon which they fall.
• The carbon dioxide in the atmosphere will trap a portion of these infra red radiations which are radiated back from the earth.
• This will help to maintain warmth on the surface of earth. And it is called the green house effect.
• But if the quantity of carbon dioxide increases too much in the atmosphere, greater portion of the infra red radiations will get trapped.
• This will increase the temperature of the earth beyond normal. This is called global warming.
■ Global warming causes many serious problems. Some of them are:
• Rise in sea levels due to the melting of polar ice caps and glaciers
• Increase in wild fires
• Increase in heat waves during summer
• Overall change in climate
• Disruption to agriculture due to shortage of rainfall
• Greater number of people affected by diseases
• Disruption to animal and plant life
• But if
♦ the quantity of carbon is more when compared to the quantity of oxygen OR
♦ the quantity of oxygen is less when compared to the quantity of carbon,
incomplete combustion of carbon will take place.
• This incomplete combustion will lead to the formation of carbon monoxide.
■ To avoid incomplete combustion, we must always provide proper ventilation for engines that uses combustion of fuels.
■ Also properly maintain all engines and equipments in good condition. Take all safety precautions and strictly follow instruction manuals.
Uses of carbon monoxide
Though carbon monoxide is poisonous, it has several uses. Some of them are:
• Used as a gaseous fuel • Used to produce industrial gases like water gas and producer gas • Used as a reducing agent in metallurgy
Carbonates and bicarbonates
• These are also compounds of carbon
• Marble, which is calcium carbonate (CaCO3 ), and Baking soda which is Sodium bicarbonate (NaHCO3) are examples
• They react with acids. We saw the details here.
• So reactions with acids can be used to identify carbonates and bicarbonates
In the next section, we will learn about Subshell electronic configuration.
■ Isotopes are atoms of the same element, having same atomic number Z, but different mass number A
• They will have the same Z because, the number of protons in all those atoms will be the same
• They have different mass numbers because, the number of neutrons will be different.
• We saw the details earlier here.
■ Carbon-12, carbon-13 and carbon-14 are the different isotopes of carbon.
• 99% of the carbon that occurs in nature is in the form of carbon-12
♦ The mass of carbon-12 atom is taken as the reference for expressing the atomic masses of other elements. We saw details here.
• Carbon-14 is a radioactive isotope. The presence of this isotope in a material can be used to determine the age of that material. This method of determining age is called carbon dating.
Compounds of Carbon
• Earlier in this chapter, we saw hydrocarbons. They are compounds of carbon which are formed when carbon combines with hydrogen
• Now we will see those compounds which are formed when carbon combines with some other elements
Carbon dioxide
• Carbon dioxide is a gas present in the atmosphere. It is produced mainly by the combustion of fuels.
■ How is carbon dioxide produced when combustion of fuels takes place?
• The fuels contain carbon or 'compounds of carbon'
• When the fuels burn, this carbon or ‘compounds of carbon’ reacts with oxygen. This reaction produces carbon dioxide. Let us see the equations:
• Reaction of carbon with oxygen:
C + O2 → CO2
• Reaction of a 'compound of carbon' with oxygen:
CH4 + 2O2 → CO2 + 2H2O
Properties of Carbon dioxide
• It is colourless • It does not support combustion • It is denser than air • It is odourlessCarbon dioxide cycle
The carbon dioxide in the earths atmosphere is continuously recycled. Let us see how this recycling occurs:• During photosynthesis, plants take in carbon dioxide from the atmosphere.
• They use it to prepare food. Thus the carbon becomes part of the plant body.
• These plants are eaten by animals. Then the carbon becomes part of the animal body.
• When the animals respire, they take in oxygen. The carbon in their body is given out as carbon dioxide.
• Thus the carbon dioxide enters back into the atmosphere.
Another way:
• When the plants and animals decay, they are converted into coal and petroleum. These are fossil fuels.
• When these fossil fuels are burnt, carbon dioxide is produced. In this way also, the carbon dioxide enters back into the atmosphere.
Uses of carbon dioxide
• Used in fire extinguishers• Used to make soda water and soft drinks
• Used in the manufacture of washing soda and baking soda
• Used in the manufacture of chemical fertilisers like urea
• Used in carbogen (95% oxygen and 5 % carbon dioxide) used for artificial respiration
• The solid form of carbon dioxide is called dry ice. It is used as a refrigerant and also to create stage effects resembling clouds
Green house effect and Global warming
• In the sunlight that the earth receives, infra red rays and ultra violet rays are also present.• The infra red rays are thermal radiations. They are referred to as heat waves also. Because they tend to increase the temperature of substances upon which they fall.
• The carbon dioxide in the atmosphere will trap a portion of these infra red radiations which are radiated back from the earth.
• This will help to maintain warmth on the surface of earth. And it is called the green house effect.
• But if the quantity of carbon dioxide increases too much in the atmosphere, greater portion of the infra red radiations will get trapped.
• This will increase the temperature of the earth beyond normal. This is called global warming.
■ Global warming causes many serious problems. Some of them are:
• Rise in sea levels due to the melting of polar ice caps and glaciers
• Increase in wild fires
• Increase in heat waves during summer
• Overall change in climate
• Disruption to agriculture due to shortage of rainfall
• Greater number of people affected by diseases
• Disruption to animal and plant life
Carbon monoxide
• We have seen that, when carbon reacts with oxygen, carbon dioxide is produced• But if
♦ the quantity of carbon is more when compared to the quantity of oxygen OR
♦ the quantity of oxygen is less when compared to the quantity of carbon,
incomplete combustion of carbon will take place.
• This incomplete combustion will lead to the formation of carbon monoxide.
■ To avoid incomplete combustion, we must always provide proper ventilation for engines that uses combustion of fuels.
■ Also properly maintain all engines and equipments in good condition. Take all safety precautions and strictly follow instruction manuals.
Uses of carbon monoxide
Though carbon monoxide is poisonous, it has several uses. Some of them are:
• Used as a gaseous fuel • Used to produce industrial gases like water gas and producer gas • Used as a reducing agent in metallurgy
Carbonates and bicarbonates
• These are also compounds of carbon
• Marble, which is calcium carbonate (CaCO3 ), and Baking soda which is Sodium bicarbonate (NaHCO3) are examples
• They react with acids. We saw the details here.
• So reactions with acids can be used to identify carbonates and bicarbonates
In the next section, we will learn about Subshell electronic configuration.
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