If you deal with large numbers like the mass of electron
0. 000 000 000 000 000 000 000 000 000 000 000 910 938 291 kg
handling this kind of numbers is very large, a convenient way of writing such as this number is to use scientific notation.
in scientific notation, the mass of electron is:
9.10 938 291 x 10 ^ -31
or
9.11 x 10 ^ -31
