In section 3.1.3 we
learned about mass
numbers. The mass number of an atom is a whole number,
and is obtained by adding the number of protons and neutrons
in the nucleus of the atom. Since protons and neutrons are the heaviest
of the three types of subatomic particles, the mass number of an atom is very
close to the mass of the atom.
The periodic table of elements SHOWS you
the atomic mass of each element. Note that atomic
mass is NOT a whole number! Take a look at the periodic table closely
to verify the atomic mass for the first 10 elements
by clicking on the symbol of the element.
The unit of atomic
mass of an atom is atomic mass unit.If you are unfamiliar with this unit of mass, it can be converted
to the SI unit of gram.
1 amu = 1.67 x 10-24 gram
6.02 x 1023 amu = 1 gram
Atomic mass unit is used to describe the mass of
very tiny objects like an atom.