Hydrocarbon molecules contain covalent bonds.

1. (a)Define covalent bond.[1]
2. (b)A C=C bond in an alkene is made from a σ bond and a π bond.
3. (b)(i)Identify the hybridisation of the carbon atoms in a C=C bond in an alkene.[1]
4. (b)(ii)Draw labelled diagrams to show, in terms of orbital overlap, how the σ and π bonds are made in a C=C bond. σ bond π bond[2]
5. (c)In electrophilic reactions involving alkenes the π bond of C=C is broken.
6. (c)(i)Suggest one difference between σ and π bonds that explains why the π bond is broken in electrophilic addition reactions involving alkenes.[1]
7. (c)(ii)Complete [Figure 5.1] to show the mechanism for the electrophilic addition of hydrogen bromide to 2-methylpropene to produce the major organic product. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. H CH3 H–C=C–CH3 H–Br [Figure 5.1][4]

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