Question

The melting point of AlF₃ is 104º C and that of SiF₄ is - 77º C (it sublimes) because : 

(A) there is a very large difference in the ionic character of the Al - F and Si - F bonds 

(B) in AlF₃ , Al³⁺ interacts very strongly with the neighbouring  F^- ions to give a three dimensional structure but in SiF₄ no such interaction is possible 

(C) the silicon ion in the tetrahedral SiF₄ is not shielded effectively from the fluoride ions whereas in AlF₃ , the  Al³⁺ ion is shielded on all sides 

(D) the attractive forces between the SiF₄ molecules are strong whereas those between the AlF₃ molecules are weak

Answer 1

Correct Answer : B. in AlF₃ , Al₃⁺ interacts very strongly with the neighbouring F^- ions to give a three dimensional structure but in SiF₄ no such interaction is possible