Answer: F- is smaller than Cl-, so Na-F distance is shorter and lattice energy (alpha 1/r) is higher.
- A F- is smaller than Cl-, so Na-F distance is shorter and lattice energy (alpha 1/r) is higher
- B Fluoride ion generally has a lower atomic mass than chloride ion under typical conditions
- C Sodium ion is somehow larger when paired specifically with fluoride according to standard textbooks
- D NaF possesses significant covalent character unlike NaCl in general practice as frequently described
Correct answer: A. F- is smaller than Cl-, so Na-F distance is shorter and lattice energy (alpha 1/r) is higher
Explanation: Lattice energy ∝ (q+×q-)/(r+ + r-). F- is smaller than Cl-, decreasing internuclear distance and increasing lattice energy.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.