An acid is a substance which ionises (splits into ions) when placed in water, producing hydrogen ions (H + ) E.g. Sulfuric acid H 2 SO 4 H + + HSO 4 - Acids are classified as strong or weak depending on the number of H + ions produced when in water.

Ethanoic acid, citric acid, and tartaric acid are classified as weak acids because less than 100% of their molecules ionise when placed in water. Hydrochloric (HCl), sulfuric (H 2 SO 4 ), and nitric acids are classified as strong acids because 100% of their molecules ionise when placed in water.

Acid + Metal __________ + ___________ __________ + ___________ Acid + Carbonate ________ + ________ + ________ ________ + ________ + ________ HCl + Fe Iron metal Hydrochloric acid HCl + CaCO 3 Calcium carbonate Hydrochloric acid

Acid + Bicarbonate _______ + _______ + _______ _______ + _______ + _______ HCl + NaHCO 3 Calcium carbonate Hydrochloric acid Bicarbonates have the same products as carbonates when reacted with acids. Bicarbonates just have an extra ‘H’ Bicarbonate ion: HCO 3 - Carbonate ion: CO 3 -

Elements: Substances made up of 1 type of atom, e.g. diamond (C only). A # = # of p (= to # e-) M # = # of p + # of n + + e- Symbol Arranged in P.T. in order of A # Groups (e- config) Periods (# E levels) p (+ve) 1 st E level n ( Ø ) e- (-ve) [O.N.E] Atoms e- arrangement E level Max # e- Each element in period = same # E levels for e-s. 1 st + last element = v. diff. b/c diff. in e- + p # Elements in same group = similar properties b/c all have same # of e- in v.E level e- 17p 18n e- 3 rd shell (also v.shell) e- arrangement e.g.Cl atom: 2, 8, 7 Cl- ion: 2, 8, 8 p = 17; e = 17; n = 18 e- 11p 12n e- Na Atoms lose or gain e- in order to achieve a full v.shell and ∴ be in a lower, more energetically favourable state e- 17p 18n e- p = 11; e = 11; n = 12 Cl nucleus (p + n) { 1 st shell (or E level) 2 nd shell Shells/ E levels: Found at diff. distances from nucleus Ion formation: Atoms become ions. Ion = atom w/ + or – electrical charge. e- is transferred e- 11p 12n e- Na + p = 11; e = 10; n = 12 p = 17; e = 18; n = 18 Cl - Ion charge = diff. in p & e- # e.g. Cl - = 1 more -ve e- than +ve p. ∴ charge = 1- Ions Ionic compounds (salts): Ions with oppos. charges are electrostatically attracted to one another. Na + Cl - e.g. Ion w/ 1 +ve charge is ∴ electrostatically attracted to an ion w/ 1 –ve charge ( ∴ 1:1 ratio) NaCl Chemical formula Must be in correct order and ratio Metal 1 st Non-metal 2 nd 1:1 ratio (Polyatomic ions)* brackets OH - NO 3 - HCO 3 - SO 4 2- CO 3 2- NH 4 + Shows amount of atoms in substance, e.g. 1 Na + and 1 Cl - Indicators: Used to indicate if substance = acid or base. They ∆ colour according to pH. e.g. litmus/ U.I ∆ colour depending on amount of OH - / H + produced Acids # indicating acidity/alkalinity Ionises to produce H + ions when placed in H 2 O Weak/ dilute. a c : produce small amounts of H +. (<100% ionise). Strong/ conc. a c : produce large amounts of H +. (100% ionise). e.g. H 2 SO 4 → H + + HSO 4 - (Put in H 2 O) Strong a c = many H + produced. Many H + turn U.I red Reactions