Negative charge is the answer
Formula to find the percent composition of an element in a compound is

.
Now enter the variables into the formula.

%
Round to 3 significant figures. 15.897% = 15.9%
The answer is 15.9% H
Yes, it is possible if the death rate exceeds that of the birth rate. This death rate could be due to a dramatic change in climate, health issues in a population, etc.