Which pair of elements would form a nonpolar covalent bond? a. bismuth and sulfurb. carbon and oxygenc. nitrogen and oxygend. silicon and phosphoro

Answer is: D.silicon and phosphorus.

When the electronegativity difference is greater, the bond polarity is increasing..  

Electronegativity (χ) is a property that describes the tendency of an atom to attract a shared pair of electrons.  

Atoms with higher electronegativity attracts more electrons towards it, electrons are closer to that atom.  

A) Δχ(Bi-S) = 2.5 - 2.0 = 0.5; polar covalent.

B) Δχ(C-O) = 3.5 - 2.5 = 1.0; polar covalent.

C) Δχ(N-O) = 3.5 - 3 = 0.5; polar covalent.

D) Δχ(Si-P) = 2.2 - 1.9= 0.3; nonpolar covalent.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.