Recall that the melting point of a metal is related to its lattice energy.
The lattice energy can be estimated using:
This means the metal with the lowest lattice energy has the lowest melting point.
Since all of the given metals are from Group 1A, the charge is the same for all of them.
Therefore, the lattice energy will just depend on the atomic radius:
higher atomic radius → lower lattice energy → lower melting point
Recall that the trend for atomic radius is as follows: it increases from right to left and down a group in the periodic table.
Which would you expect to have a higher melting point: sodium chloride, NaCl, or cesium chloride, CsCI? Why?
A. The cesium chloride has a higher melting point because larger ions of the same charge are able to attract more ions of the opposite charge.
B. The cesium chloride has a higher melting point because its ions are smaller, which makes the charges more dense.
C. The sodium chloride has a higher melting point because of the greater charges of the ions, and hence the greater force of attractions between them.
D. The sodium chloride has a higher melting point because its ions are smaller, which allows oppositely charged ions to get closer.
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