Neco 2020 Chemistry Question 26

Given the following data for two ionic compounds: - LiF: electronegativity of Li = 0.98, of F = 3.98; ionic radii Li⁺ = 0.076 nm, F⁻ = 0.133 nm. - NaCl: electronegativity of Na = 0.93, of Cl = 3.16; ionic radii Na⁺ = 0.102 nm, Cl⁻ = 0.181 nm. (a) Using the formula \(\%\,\text{ionic character}= \left(1- e^{-0.25(\Delta\chi)^2}\right)\times100\), calculate the percent ionic character of each compound. (b) Assuming lattice energy is proportional to \(\dfrac{z^{+}z^{-}}{r^{+}+r^{-}}\) (where \(z^{+},z^{-}\) are the ionic charges and \(r^{+}, r^{-}\) the ionic radii), determine which compound has the higher lattice energy. State the compound that has both the greater percent ionic character and the higher lattice energy.