1 Consider the first atom of each part of the molecule. An atom with higher atomic number has higher priority. (e.g. I > Cl > C > H)  If the first atom of two groups is the same, consider the second atom(s) in the same way as the first. (e.g. -C(CH3)3 > -CH(CH3)2 > -CH2CH3 > -CH3).
1 You can also use a toilet plunger on your bathroom sink. 2  Fill up the sink with water first, the use the plunger vigorously on the drain just as you would a toilet. 3  This will lift and agitate any blockage in the drain. It will smell a bit like vinegar for about a day. 2  You can also use a toilet plunger on your bathroom sink. 3  Fill up the sink with water first, the use the plunger vigorously on the drain just as you would a toilet.
The giant finger blocking your roof vent could be ice or snow or debris or even an animal carcass. The result? Whenever a lot of water goes down the drain, it sucks the water out of your toilet and maybe out of the traps under your sinks. The blockage probably makes your tub drain pretty slowly, too. A plumber can remove an obstruction by running a snake from the roof down your vent system, but to keep it from happening again, you have to figure out what's causing it.