2.1 Relative atomic & molecular mass, Avogadro's constant...

• Relative atomic mass (Ar) is the weighted average mass of an atom of an element, taking into account its naturally occurring isotopes, relative to 1/12 of the mass of an atom of carbon-12.
• Relative molecular mass (Mr) is the mass of that molecule relative to 1/12 the mass of an atom of carbon-12.
• The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12. (These particles could be ions, atoms, molecules or electrons)
• No. of particles = no. of moles x Avogadro's constant
• Mr x moles = mass (in grams)