Fundemental particles

Characteristics of protons, neutrons, electrons

Whats mass number

number of protons + neutrons

Atomic number

number of protons or electrons

Whats an isotope

atoms of the same element with the same number of protons but different numbers of neutrons.

Properties of isotopes

Chemical properties are the same, determined by having the same number of electrons

Whats Ar

The Ar of an element is the average mass of an atom relative to 1/12 the mass of one atom of carbon-12. This is why the Ar is frequently not a whole number.

Whats relative atomic mass of an atom

The average mass of an atom of an element when measured on scale on which the mass of the atom of 12^C is exactly 12

Whats the relative atomic mass of a molecule

 the average mass of a molecule when measured on a scale on which the mass of an atom of 12^C is exactly 12.

Relative isotopic mass

 the mass of an isotope of an element measured on scale on which the mass of an atom 12^C is exactly 12.