Question

the ionic compounds nacl and mgs are represented by the diagrams above. which statement correctly identifies diagram 1 and identifies the compound with the lower melting point, explaining why?

a diagram 1 represents nacl; it has a lower melting point than mgs has because the coulombic attractions between the singly charged na+ ions and the cl- ions in nacl are stronger than those between the ions in mgs.

b diagram 1 represents nacl; it has a lower melting point than mgs because the coulombic attractions between its singly charged na+ ions and the cl- ions are weaker than those between the ions in mgs.

c diagram 1 represents mgs; it has a lower melting point than nacl because the coulombic attractions between its doubly charged mg²+ ions and the s²- ions are stronger than those between the ions in nacl.

Explanation:

Ionic compounds' melting points depend on the strength of coulombic attractions between ions. Coulomb's law (\(F = k\frac{q_1q_2}{r^2}\), where \(q_1\) and \(q_2\) are ion charges, \(r\) is the distance between ions) shows that higher - charged ions have stronger attractions. \(Na^+\) and \(Cl^-\) have \(+ 1\) and \(-1\) charges. \(Mg^{2 + }\) and \(S^{2 - }\) have \(+2\) and \(-2\) charges. Stronger attractions mean higher melting points. So, \(NaCl\) (with lower - charged ions) has weaker coulombic attractions and a lower melting point than \(MgS\).

Answer:

B. Diagram 1 represents \(NaCl\); it has a lower melting point than \(MgS\) because the coulombic attractions between its singly charged \(Na^{+}\) ions and the \(Cl^{-}\) ions are weaker than those between the ions in \(MgS\).