Atomic mass is the mass of one atom of an element compared with 1/12th of the mass of a carbon-12 atom
It is usually expressed in atomic mass unit (u)
To find atomic mass, check the element’s atomic mass from the periodic table
For a single atom, atomic mass is the relative mass given in the periodic table
For compounds, add the atomic masses of all atoms present in the formula
Example: H2O = 2 × atomic mass of H + 1 × atomic mass of O
Example: CO2 = 1 × atomic mass of C + 2 × atomic mass of O
For isotopes, use the mass number as the atomic mass if needed for class 9 level
Atomic mass is not the same as atomic number
Atomic number = number of protons
Atomic mass = protons + neutrons in an atom, approximately