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CBSE Class 10 Science, Revision Notes, CHAPTER - 4, CARBON AND ITS COMPOUNDS, , © Carbon is a versatile element. Found in .02% in form of minerals an 03% in form of, CO2, , e All living structures are carbon based., Covalent Bond in Carbon, , ¢ The atomic number of carbon is 6 and its electronic configuration is 2, 4. To attain a, noble gas configuration it requires four more electrons in its valence shell., , ¢ Itis difficult for an atom of carbon to either gain or lose electrons as it would be, difficult to hold extra electrons and would require a large amount of energy to, remove four electrons., , ¢ Carbon attains the noble gas configuration by sharing its valence electrons with other, atoms.Such mutual sharing of electrons between atoms to attain a stable noble gas, configuration is called Covalent bonding., , e Atoms of other elements like hydrogen, oxygen, nitrogen, chlorine also show sharing, of valence electrons., , ¢ Depending on the number of electron pairs shared, covalent bond is of three types :, , 1. Single Covalent Bond: Single covalent bond is formed because of sharing of two, electrons,i.e one pair .Example : Hydrogen,Chlorine,Methane., , 2. Double covalent bond: Double bond is formed by sharing of four electrons,i.e two pairs, of electrons. Example : Oxygen molecule,Carbon Dioxide molecule., , 3. Triple Covalent Bond: Triple covalent bond is formed because of the sharing of six, electrons, three pairs of electrons. Example :Nitrogen,C,H»
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=, |, , 1. CATENATION is property of carbon atom to form bond with other atoms of carbon. Like, carbon, silicon forms compounds with hydrogen upto seven or eight atoms of silicon called, silanes., , , , 2.TETRA VALENCY : Having a valency of 4, carbon atom is capable of bonding with, , atoms of oxygen, hydrogen, nitrogen, sulphur, chlorine and other elements. Since it requires, four electrons , carbon is said to be tetravalent., , The smaller size of carbon atom enables nucleus to hold the shared pair of electrons, strongly, thus carbon compounds are very stable in general., , HYDROCARBONS: The compounds which are majorly made of hydrogen and carbon, atoms.Hydrocarbons are further classified as
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Saturated and Unsaturated Carbon Compounds, , Saturated Compounds : Saturated compounds are hydrocarbons in which hydrogen and, carbon have single bonds. They are also known as Alkanes., ALKANE : C;,Hon.+2, , Unsaturated Compounds : hydrocarbons in which hydrogen and carbon have double or, triple bonds. hydrocarbons with double covalent bonds are alkenes and those with triple, covalent bonds are alkynes., , ALKENE : C,H", , Note : alkene does not exist with one carbon atom, thus, methene does not exist., , ALKYNE : C;,Hon—2, note : minimum two carbon atoms are required to form alkyne., , Apart from branched structures, carbon compounds are present in cyclic form. Example:, Electron Dot structure :Lewis structures (\electron dot structures) are diagrams that show, the bonding between atoms of a molecule and the lone pairs of electrons that may exist in, the molecule., , Steps to draw a Lewis structure :, , 1. Decide how many valence (outer shell) electrons are possessed by each atom in the, molecule., , 2.If there is more than one atom type in the molecule, put the most metallic or least, electronegative atom in the center. Recall that electro-negativity decreases as atom moves, further away from fluorine on the periodic chart., , 3.Arrange the electrons so that each atom contributes one electron to a single bond between, each atom., , 4.Count the electrons around each atom: are the octets complete? If so, your Lewis dot, structure is complete., , 5. If the octets are incomplete, and more electrons remain to be shared, move one electron, per bond per atom to make another bond. Note that in some structures there will be open, octets (example: the B of BF3), or atoms which have ten electrons (example: the S of SFs), , 6. Repeat steps 4 and 5 as needed until all octets are full., 7. Redraw the dots so that electrons on any given atom are in pairs wherever possible.
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Electron dot structure of a saturated carbon compound, ethane is as follows:, , , , Electron dot structure of an unsaturated carbon compound, ethene is as follows:, , EOD, , TRY DRAWING THE ELECTRON DOT STRUCTURE OF ETHYNE, , Formulae and Structures of Saturated Compounds of Carbon and Hydrogen, , , , , , , , , , , , , , No. of, Carbon Name Formula Structure, Atoms, H, I, 1 Methane CH, H=C = 5, ', H, H H, t i, 2 Ethane CH, x= 5 = 7 =H, H H, H H H, | |, 3 Propane C\H, H=-C-C-C-H, i ot ot, H HH, H H H H, Le, 4 Butane Ca. H=C=-C=-C -—¢€ =<, I =, H H H H, H H H H H, hl 8 ! |, 5 Pentane CH, |x—C=-C-¢c—¢—¢ =F, fi 4 I |, H H H H H
