(a) What are \(trihalomethanes\) (THMs)? (b) Draw the Lewis structures of two example THMs.

Trihalomethanes (THMs) are a group of organic chemical compounds that consist of one carbon atom, one hydrogen atom, and three halogen atoms (such as chlorine, bromine, or iodine). THMs are formed as a byproduct when chlorine or other disinfectants are used to treat water, which reacts with naturally occurring organic matter in water. They are common water contaminants and can have negative health effects if present at high levels.

In order to draw the Lewis structures of two example THMs, we should first choose two examples of THMs and then draw their respective Lewis structures. Example 1: Chloroform (CHCl₃) 1. Count the total number of valence electrons: \(6 (from C) + 1 (from H) + 3 \times 7 (from Cl) = 28\). 2. Place the carbon atom in the center since it is less electronegative than chlorine, and connect all other atoms to the central atom with single bonds. 3. Complete the octets of the outer atoms (chlorine) by adding lone pairs of electrons. 4. Calculate the formal charge if necessary and adjust the bonding patterns as needed (in this case, no adjustment is needed). Lewis structure of Chloroform: Cl \ C - H / Cl Example 2: Bromoform (CHBr₃) 1. Count the total number of valence electrons: \(6 (from C) + 1 (from H) + 3 \times 7 (from Br) = 28\). 2. Place the carbon atom in the center since it is less electronegative than bromine, and connect all other atoms to the central atom with single bonds. 3. Complete the octets of the outer atoms (bromine) by adding lone pairs of electrons. 4. Calculate the formal charge if necessary and adjust the bonding patterns if needed (in this case, no adjustment is needed). Lewis structure of Bromoform: Br \ C - H / Br