Chemistry - Definitions - OCR

Relative atomic mass: 

 the weighted mean mass of an atom of an element compared to 1/12 th of the mass of C-12 whose mass is exactly 12.

Relative isotopic mass:

the mass of an atom/isotope compared to 1/12th of the mass of an atom of C-12.

Relative molecular mass:

the weighted mean mass of a molecule of a substance compared to 1/12th of the mass of C-12 whose mass is exactly 12.

Relative formula mass:

the weighted mean mass of the formula unit compared to 1/12th of the mass of an atom of C-12

Empirical formual:

simplest whole number ratio of atoms in a compound

Molecular formula:

actual numbers of atoms of each element in a molecule

Atomic number

the number of protons in an atom or ion of an element

Mass number

number of protons and neutrons in the nucleus of an atom

Isotopes

atoms of the same element with a different mass. The isotopes of an element…