Covalent structures and bonding
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I have 3 questions.
1) A low boiling point is evidence that propane is molecular. If it was liquefied under pressure, what would you expect an electrical conductivity test to show?
2) What difference in the covalent bonding in propene compared to propane?
3) What's a 'dot & cross' diagram?
thanx alot for ur help!!
Corrie writes ......
1. Yes, propane (C3H8) is composed of separate, non-polar molecules. Therefore in the gaseous, liquid or solid state there are no ions or mobile electrons present, so propane won't conduct electricity in any state, even under pressure.
2. Propane (C3H8) is an alkane and contains only C-C and C-H covalent bonds. Propene (C3H6) is an alkene and contains a C=C double covalent bond, as well as a C-C bond and C-H bonds.
3. 'Dots & crosses' are used to represent the outer electrons in different atoms and show how are paired up to form single, double or triple covalent bonds, or non-bonding pairs. 'Dots' (or 'o's) are used for the electrons in one atom, 'crosses' (or 'x's) for the electrons in the other atom.
Thus a simple single covalent bond between an H-atom and a Cl-atom in a HCl molecule would be represented by a 'dot' and a 'cross' placed together between between the two atoms:
Obviously there are not really different kinds of electrons, we just use 'dots' and 'crosses' to distinguish which atoms in a molecule they originally came from. A covalent bond is represented by a 'dot' and a 'cross' together, a non-bonding pair of electrons by a pair of 'dots' or a pair of 'crosses'.
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updated: 11 November 2007
