Do you mean scientific notation?
If so, you move the decimal place to the right in order to create a whole number.
0.000000000005 would require you to move the decimal place 12 times to get the number 5.
The number of times you move the decimal place becomes the exponent. Because this number was originally a decimal and we had to move the decimal to the right, 12 has to be negative (-12). In scientific notation we use 10 as the base.
In scientific notation this number would become:
5 x 10^-12
