The electronegativities of four elements are given in the table.

Which statement is correct?

A.     W and X form an ionic compound.

B.     W and X form a covalent compound.

C.     Y and Z form an ionic compound.

D.     Y and Z form a covalent compound.

D

Some teachers commented that two answers were acceptable as the difference of electronegativity between W and X and between Y and Z were both small, which could indicate a covalent bond. Although the students did not have access to the data booklet, the values of electronegativity of W and X were much smaller than those for Y and Z, indicating that they were metals. However, in fairness to the candidates it was decided to accept both answers B and D.