Unit 2: Section 2 - Group 2 and Group 7 elements

Increases - extra electron shells are added

Decreases 1. Each element has an extra electron shell as you go down 2. This extra inner shell shields the outer electrons from the attraction of the nucleus 3. The electrons are also further away from the nucleus, which greatly reduces the nucleus’ attraction 4. Both of these factors make it easier to remove outer electrons, resulting in a lower first ionisation energy

Increases 1. As you go down the group, first ionisation energy decreases due to the increasing atomic radius and shielding effect 2. When group 2 electrons react, they form +2 ions by losing electrons 3. The lower the first ionisation energy, the more reactive the element, as it’s easier to lose outer shell electrons

Decreases 1. They have typical metallic structures with positive ions in a crystal structure surrounded by delocalised electrons 2. Down the group the metal ions get bigger but the number of delocalised electrons per atom doesn’t change and neither does the charge on the ion 3. The larger the ion and the further away the delocalised electrons are from the positive nuclei, the less attraction they feel 4. It takes less energy to break the bonds 5. Mg is an anamoly becsause the crystal structure changes

They are oxidised from a state of 0 to +2 froming M2+ ions - react with water to form a metal hydride and hydrogen

• Compounds that contain singly charged negative ions increase in solubility down the group • Compounds that contain doubly charged negative ion decease in solubility down the group OH- hydrOxides are mOre sOluble dOwn SO42- suLfates are Less soLuble down Magnesium is sparingly soluble and most sulfates are soluble in water but BaSO4 is insoluble

Acidify the solution with hydrochloric acid to remove any carbonates which will also produce a white precipitate Add acidified barium chloride (BaCl2) and if sulfate ions are present, a white precipitate of barium sulfate is formed

Neutralising acids 1. Calcium hydroxides (Slaked lime Ca(OH)2) - agriculture to neutralise acid soils 2. Magnesium hydroxide (Mg(OH)2) - indigestion tablets as an antacid which removes excess stomach acid

H+(aq) + OH-(aq) -> H2O(l)

• It is opaque to X-rays so is used in barium meals to help diagnose problems with the oesophagus, stomach or intestines • A patient swallows the barium meal, which is a suspension of barium sulfate • The barium sulfate coats the tissues, making them show up on the X-rays, showing the structure of the organs

• The main titanium ore, titanium (IV) oxide (TiO2) is first converted to titanium (IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas • The titanium chloride is then purified by fractional distillation, before being reduced by magnesium in a furnace of about 1000°C

TiCl4(g) + 2Mg(l) -> Ti(s) + 2MgCl2(l)

• Burning fossil fuels to produce electricity also produces sulfur dioxide, which pollutes the atmosphere • The acidic sulfur dioxide can be removed from flue gases by reacting with an alkali - wet scrubbing • Powdered calcium oxide (lime, CaO) and calcium carbonate (limestome, CaCO3) can both be used • A slurry is made by mixing the calcium oxide or calcium carbonate with water which is then sprayed onto the flue gases • The sulfur dioxide reacts with the alkaline slurry and produces a solid waste product - calcium sulfate

CaO(s) + 2H2(l) +SO2(g) -> CaSO3(s) + 2H2(l) CaCO3(s) + 2H2O (l) + SO2 (g) -> CaSO3(s) + 2H2O(l) + CO2(g)

Fluorine - F2 pale yellow gas Chlorine - Cl2 green gas Bromine - Br2 red-brown liquid Iodine - I2 grey solid

Increases - the size and relative mass of the molecules increases therefore the Van der Waals forces also increase in strength

Decreases - they are all highly electronegative but larger atoms attract electrons less than smaller ones as the electrons are further from the nucleus and are shielded by more electrons

When the halide ion is less reactive - a halogen will displace a halide from solution if the halide is below it in the periodic table

Less oxidising down the group as they are less reactive

Cl2(aq) + 2Br-(aq) -> 2Cl-(aq) + Br2(aq) Cl - displace Br and I Br - displace I I - no reaction

Displacement reactions https://www.savemyexams.com/gcse/chemistry_combined-science/aqa/18/revision-notes/1-atomic-structure–the-periodic-table/1-2-the-periodic-table/1-2-6-group-7-the-halogens/ Learn the summary table of the displacememnt reactions of the halogens

By mixing chlorine gas with cold, dilute, aqueous sodium hydroxide which forms sodium chlorate(I) soultion 2NaOH(aq) + Cl2(g) -> NaClO + NaCl(aq) + H2O(l) Oxidation states of chlorine: 0 +1 -1 Disproportionation reaction

Water treatment, to bleach paper and textiles, cleaning

A disproportionation reaction occurs End up with a mixture of chloride anf chlorate(I) ions Cl2(g) + H2O(l) <-> 2H+(aq) + Cl-(aq) + ClO-(aq) In sunlight chlorine can also decompose water to form chloride ions and oxygen 2Cl2(aq) + 2H2O(l) <-> 4H+(aq) + 4Cl-(aq) + O2(g)