Practice question · Multiple choice
Magnesium oxide melts at 2852 °C while sodium fluoride melts at 993 °C, despite similar ion sizes. What accounts for the difference?
Hints
- Lattice energy scales with the product of the two ionic charges.
- MgO is 2+ with 2-, NaF is 1+ with 1-, so the product is 4 against 1.
Show the answer
C. MgO ions carry double charges, so lattice energy is about four times larger
Why
Lattice energy goes as . Going from to multiplies the charge product by four at comparable spacing, and that dominates the melting point.
Practise Chemical Bonds and Electronegativity
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