Which of these molecules are polar and why?

Question

1. CH4

2. CH3Br

3. CH2Br2

4. CHBr3

5. CBr4

Answer 1

Polar molecules are molecules which have different charges at different ends.  Water for example is polar because the oxygen atom is slightly negatively charged (due to electronegitivity differences) while the hydrogen atoms are slightly positively charged.

1.  CH4 is not polar, the 4 hydrogen atoms surround the carbon such that  there is no charge imbalance across the molecule.

2.  CH3Br is slightly polar because of a difference in electronegativity between C and Br

3.  Is also slightly polar for the same reason as above

4.  Is also slightly polar (see above)

5.  Is not polar for the same reason as CH4