Question

What is the total number of atoms in the formula below? NH3 one two three four

Answer 1

4
There is N, and H3. The 3 indicates that there are "3" atoms. If an atom has no letter, such as N, then it is 1. So, you could say N1H3. 

Answer 2

The formula of the substance is:

$NH_3$

So, in this substance we have:

- 1 atom of nitrogen (N), since it has no subscript, it means we have only 1 atom

- 3 atoms of hydrogen (H), since it has subscript 3

so, the total number of atoms in the substance is

1+3=4

And the correct answer is four.