chem / Chem.mdon commit planner (a589bb9)
   1- Relative isotopic mass - mass of an isotope (compared to Carbon-12)
   2- Atomic number (protons) is constant between isotopes - defines element.
   3- Mass number - number of nucleons (defines isotope)
   4- Relative atomic mass - average mass: $A_r = {{RIM \times abundance} \over 100}$
   5- Relative atomic mass ($M_r$) - sum of relative atomic masses
   6- Mole $6.02 \times 10^{23}$ (= no of atoms in Carbon-12) $=N_A$ (Avogadro's constant)
   7- Molar mass - physical mass of 1 mol of a substance ($6.02 \times 10^{23}$ atoms)
   8  - Unit: grams / mole
   9
  10$$
  11n = {m \over M}