Question

How many negative charges are in the atom

Answer 1

The number or electrons (negative charges) is equal to the number of protons (positive charges). If they weren't equal i.e. if there were more electrons or protons then the atom would become an ion. So the answer is, it depends on the element... look at a periodic table. 

Answer 2

subtract the number of protons (the atomic number) from the mass number to get how many neutrons there are, and the number of neutrons is the same number as the electrons which provide the negative charge