1. The simplest alkane is the gas methane, whose molecular formula is CH4. Methane exists as a tetrahedral shape, but it is often represented by a flattened structure as are most organic compounds.
Two four-carbon alkanes are known, and they have measurably different chemical and physical properties. Their structures are H3CCH2CH2CH3 and H3CCH(CH3)2. Therefore they were named normal butane, often abbreviated as n-butane, and isobutane. The straight-chain form is considered the "normal" form. Alternatively, they could be named using the systematic IUPAC method as 1-methylpropane and 2-methylpropane, or even as butane and 2-methylpropane. The IUPAC method names the longest straight carbon chain in the usual way and then numbers the carbons; the location of a substituent group is given by the number of its carbon. The IUPAC method is always used for more complicated molecules, but many of the simpler ones still use non-systematic names, called trivial names, because these are less cumbersome to use.
2 . Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. The term "unsaturated" means more hydrogen atoms may added to the hydrocarbon to make it saturated: consisting all single bonds.
Dont know 3. Sorry!
