# How to Read Atomic Mass

## Transcript

Hello, my name is Walter Unglaub, and this is how to read atomic mass. First let me make the distinction that atomic mass does not equal relative atomic mass, nor does it equal atomic weight. Atomic mass is denoted by the symbol u, which stands for unified atomic mass unit. So by definition, one u is equal to one-twelfth the mass of a carbon-12 atom. And this in kilograms is approximately equal to 1.661 times 10 to the negative 27 kilograms. A more natural unit would be to use electron volts, which is a unit of energy, because of the rest mass energy mass equivalence equation, E equals MC-squared, we can denote the mass in terms of its rest mass energy divided by the speed of light squared. So this number in terms of units of electron volts is approximately equivalent to 931.494 mega electron volts per speed of light squared. So, if you have a certain element or a certain number of atomic mass units, you would simply multiply that number by either this number to get your mass in terms of kilograms or by this number to get your mass in terms of mega electron volts per speed of light squared. My name is Walter Unglaub, and this is how to read atomic mass.

Walter Unglaub graduated from the Colorado School of Mines with a B.S. in Engineering Physics and a M.S. Applied Physics.