Chapter 2 - Atoms, Ions + Compounds

element

a substance that is made up of one type of atom

atom

the basic unit that makes up all matter

relative atomic mass (RAM)

the weighted average mass of one atom of an element/compound relative to the 1/12 of the mass of one atom of carbon-12

weighted mean/average mass

takes into account the relative abundances of all the isotopes

molecule

simple structure made up of 2 or more atoms that are chemically combined

relative molecular mass (Mr)

used to describe simple molecules

formula unit

simplest ratio of each type of atom in a giant lattice

relative formula mass

used to describe compounds with giant structures/lattice

isotope

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

relative isotopic mass

the mass of one atom of an isotope compared with 1/12 of the mass of one atom of carbon-12

-is the same as the mass number

mass spectrometry

used to work out the relative atomic mass

-shows the percentage abundances for each isotope

-number of peaks = number of isotopes

example = chlorine - has 2 sections as chlorine is diatomic, the abundance for Cl72 is higher than normal as there are 2 different ways it can be formed 35-37 or 37-35

IONS FORMULAE -nitrate

NO₃^-

-carbonate ion

CO₃^2-

-sulfate ion

SO₄^2-

-phosphate ion

PO₄^3-

-hydroxide ion

OH^-

-ammonium ion

NH₄⁺

EXCEPTIONS of ions where their group numbers do not match their charge

-silver (Ag) = Ag⁺

-zinc (Zn) = Zn²⁺

molecular ions

groups of covalently bonded atoms that can gain or lose electrons - charge is shared out across whole molecule