Covalent bonding

Nature of science:

Looking for trends and discrepancies—compounds containing non-metals have different properties than compounds that contain non-metals and metals. (2.5) Use theories to explain natural phenomena—Lewis introduced a class of compounds which share electrons. Pauling used the idea of electronegativity to explain unequal sharing of electrons. (2.2)

• A covalent bond is formed by the electrostatic attraction between a shared pair of electrons and the positively charged nuclei.
• Single, double and triple covalent bonds involve one, two and three shared pairs of electrons respectively.
• Bond length decreases and bond strength increases as the number of shared electrons increases.
• Bond polarity results from the difference in electronegativities of the bonded atoms.

Applications and skills:

• Deduction of the polar nature of a covalent bond from electronegativity values.

Guidance:

• Bond polarity can be shown either with partial charges, dipoles or vectors.
• Electronegativity values are given in the data booklet in section 8.

• Microwaves—cooking with polar molecules.
• Syllabus and cross-curricular links:
• Topic 10.1—organic molecules

Aims:

• Aim 3: Use naming conventions to name covalently bonded compounds.