AP Chemistry Question of the Day --46

Welcome back to my blog. Here comes the answer to question 44 I posted earlier. The correct answer is B. 

When two atoms of the same element form a bond, they equally share the bonding electrons and the bond is  non polar  and the molecule is non polar, for example hydrogen in answer A. When two atoms of different elements form a bond, they do not share the bonding electron pair equally. The atom with higher electronegativity pulls the bonding electron pair closer to itself, making it partially negative and the other atom partially positive. As a result, the bond is polar.

The polarity of a molecule depends on both the polarity of the individual bond and the geometry of the molecule. If the geometry of the molecule is arranged in a way that all the dipole moments of the polar bond can cancel out, the overall molecule will appear to be non polar.

CO2 has two polar bonds, but the two dipole moments are opposite in direction and thus cancel out each other. The molecule is non polar.

Both answer C and D has outstanding dipole moments when molecular geometry has been taken into account. They are polar molecules.

Following is Question 46 of the series. 

46. Which elements have the highest electron affinity and electronegativity respectively?

A. F, F

B. F, Cl

C. Cl, Cl

D. Cl, F

I will post the answer and explanation tomorrow. 

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