Magnesium oxide (MgO) and carbon monoxide (CO) are both gaseous at high temperature, yet one contains a metal–nonmetal bond and the other a non-metal–non-metal bond. The following data are available.
Molecule
Bond length / pm
Dipole moment / D
Δχ (Pauling)
MgO
174
6.19
2.2
CO
113
0.12
1.0
Constants: 1 D = 3.34×10−30C⋅m; e=1.60×10−19C.
(a) Calculate the percent ionic character of the Mg–O bond in MgO and of the C–O bond in CO.
(b) Using the results from part (a) together with the Δχ values, analyze the extent to which electronegativity difference alone predicts bond character.
(c) Describe how the differing bond characters of MgO and CO are reflected in their macroscopic chemical behaviors, specifically:
• solubility in polar versus non-polar solvents
• electrical conductivity of their molten phases
• reactivity toward strong acids or bases.
(d) Propose an experimental measurement (other than dipole moment) that could further substantiate the ionic versus covalent nature of each bond, and explain the expected outcome for both compounds.