Chapter 8

An element that reduces other substances by losing electrons to another species

2Mg + O2 —> 2MgO

Forms alkaline hydroxide and hydrogen Mg + 2H2O —> Mg(OH)2 + H2

Metal + acid —> salt + hydrogen Mg + HCl —> MgCl + H2

The ionisation energies decrease down the group Because attraction between nucleus and outer electrons decrease • atomic radius increase • more shielding Less energy needed to remove electron More easily lost More reactive

Releases hydroxide ions, OH- Forming alkaline solutions MgO (s) + H2O —> Mg2+(aq) + 2OH-(aq)

Further metal and hydroxide ions will form a solid precipitate Mg2+ (aq) + 2OH- (aq) —> Ca(OH)2

down a group Alkalinity increases Solubility increases pH increases More OH- ions

1) add partial of each group 2 oxide to water 2) shake mixture 3) insufficient water to dissolve all metal hydroxide, undissolved white solid at bottom - saturated solution 3) measure pH Should increase down group

Used to neutralise acidic fields Ça(OH)2 (s) + H+ (aq)—> Mg2+(aq) + 2H2O Used in antacids for treating acid indegstion CaCO3 (s) + HCl (aq) —> CaCl2 (aq) + H2O + CO2 Mg(OH)2

Boiling points increase down group Because More electrons Stronger London forces More energy required to break London force

Substance that has the ability to oxidise other substances by gaining electrons

1) a solution of each halogen is added to aqueous solutions of the other halides If the halogen added is more reactive than halide then 2) a reaction takes place - displacing 3) the solution changes colour

I2 - brown Br2- orange Cl2 - pale green

Add a non polar solvent = cyclohexane Shake Halogens dissolve more readily Colours are easier to tell apart

I2- pale green Br2- orange Cl2- violet

Cl2 + Br- —> Cl- + Br2 (aq)

Fluorine - Pale yellow gas Reacts with all substances it comes into contact with Astanine - has not been seen It’s radioactive and decays rapidly

Halogens react by gaining electrons As you go down the group tendency to gain a electron decreases Because Atomic radius and shielding increases Less nuclear attraction to capture an electron from another species Reactivity decreases

Redox reaction in which the same element is both oxidised and reduced Chlorine with water and cold dilute sodium hydroxide Chlorine with dilute sodium hydroxide - dissolve more readily than in water Cl2 + 2NaOH -> NaClO + NaCl + H2O

Add dilute nitric acid (HNO3) Bubble gas through limewater (Ca(OH)2) CO2 (g) + Ca(OH)2 —> CaCO3 (s) + H2O White precipitate - milky

Add barium chloride to a solution If white precipitate formed then sulfate is present Ba2+ + SO42- —> BaSO4

0) add dilute nitric acid - remove ions that might interfere 1) add silver nitrate AgNO3 To solution 2) White cream yellow - Cl2, Br2, I2 precipitate formed 3) add aqueous ammonia to gets solubility 4) dissolves in : Cl2 - dilute ammonia Br2 - concentrated ammonia I2 - insoluble in concentrated

Carbonate CO3 2- Sulfate SO4 2- Halide Cl-