Question

draw the lewis structure of ch3br and then determine if the molecule is polar or nonpolar.

Explanation:

Step1: Calculate the total number of valence electrons

Carbon has 4 valence electrons, hydrogen has 1 valence electron (and there are 3 hydrogens), and bromine has 7 valence electrons. So the total number of valence electrons is \(4+(1\times3)+7 = 14\).

Step2: Arrange the atoms

Carbon is the central atom. Connect each hydrogen and bromine atom to the carbon atom with a single bond. Each single bond uses 2 electrons. So far, we have used \(4\times2=8\) electrons (4 bonds: 3 C - H and 1 C - Br).

Step3: Distribute the remaining electrons

We have \(14 - 8=6\) electrons left. Bromine needs 6 more electrons to complete its octet. So we place 3 lone pairs on bromine.
The Lewis structure has carbon in the center, bonded to three hydrogens and one bromine. Bromine has three lone pairs.

Step4: Determine polarity

The C - Br bond is polar (since Br is more electronegative than C). The molecule is tetrahedral in shape (approximate, due to the different atoms attached to C). The dipoles do not cancel out (because Br is more electronegative than H and there is no symmetry to cancel the C - Br dipole).

Answer:

The Lewis structure has C as the central atom with three H atoms and one Br atom bonded to it (Br has three lone pairs). The molecule \(CH_3Br\) is polar.