(b) Electronegativity is the measure of pulling power that atoms have for a shared pair of electrons in a covalent bond.

As you move down group 17 in the periodic table the electronegativity decreases because:

1. The atomic radius increases; therefore, there is less pull on the outer electrons by the nuclear charge.
2. The number of shells increases causing screening; therefore, there is less pull on the outer electrons by the nuclear charge.

(i) Shape is tetrahedral.

SiCl₄

(ii) Shape is v-shaped

SCl₂

(iii) Shape is pyramidal

PCl₃

(iv) Silicon tetrachloride

(v) Sulfur dichloride has bonds with the least degree of polarity.