Question

Define relative atomic masses(atomic weights)

Answer 1

Definition of relative atomic mass

• The relative atomic mass of an element is defined as the weight in grams of the number of atoms of the element contained in 12.00 g of carbon-12. To calculate the relative atomic mass of chlorine, the average mass of one atom of chlorine is found by considering 100 atoms of chlorine.
• It is the ratio of the average mass of atoms of an element (from a single given sample or source) to 112thof the mass of an atom of carbon-12 (known as the unified atomic mass unit)

$\therefore$Relative atomic mass is the mass of an atom of an element as a multiple of the standard atomic mass unit

For example, The relative atomic mass of an element is a weighted average of the masses of the atoms of the isotopes - because if there is much more of one isotope then that will influence the average mass much more than the less abundant isotope will. For example, chlorine has two isotopes: ${}^{35}\mathrm{Cl}$ and ${}^{37}\mathrm{Cl}$