M2S1: Atoms and Moles

Mass number

Total num proton + neutron

Atomic number

Num protons in nucleus of atom

Isotope

Isotopes of an element same num protons, diff num neutrons

Relative atomic mass

(Ar) is the weighted mean mass of the atoms of an element compared to 1/12 of the mass of carbon-12

Relative isotopic mass

Mass of an atom of any isotope of an element compared to 1/12 of the mass of an atom of carbon-12

Mass spectra

Isotopic abundance in form of graph, produced by mass spectrometers

Relative molecular mass

(Mr) is the average mass of a molecule compared to 1/12 of the mass of an atom of carbon-12

Relative formula mass

Average mass of a formula unit compared to 1/12 of the mass of an atom of carbon-12

Molar mass

• The mass of one mole of something

• (gmol^-1)

• Same numerical value as Mr

Number of moles formula

n = m/Mr

Number of gas moles (1)

n = v/24 (dm³)

Number of gas moles (2)

• pV = nRT

• v(m³)

• p(Pa)

C to K

C + 273

Number of moles in a solution

n = c x v