Period 3 periodicity

Na reaction with oxygen

Vigorous reaction that requires heat, Na burns with a bright yellow flame to produce a white solid - Na2O

Mg reaction with oxygen

Vigorous reaction, needs heat, Mg burns with a bright white flame to produce a white solid - MgO

Al reaction with oxygen

Al must be powdered (as aluminium metal is protected by a layer of aluminium oxide), then reacts with oxygen, in a fast reaction, burning with a bright white flame, to form a white powder - Al2O3

Si reaction with oxygen

Silicon must be powdered and heated strongly to react slowly with oxygen, with bright white sparkles, forming a white powder - SiO2

P reaction with oxygen

Needs heat, reacts vigorously with oxygen with a yellow or white flame to produce white clouds of P4O10

S reaction with oxygen

S must be powdered, heated then burns gently in oxygen, with a blue flame, producing toxic flames of SO2. Then further oxidation produces SO3, in a reversible reaction, with a V2O3 catalyst.

Cl reaction with oxygen

No reaction!

Na reaction with chlorine gas

Needs heat, reacts vigorously to produce solid NaCl

Mg reaction with chlorine gas

Needs heat, reacts vigorously to produce solid MgCl2

Al reaction with chlorine

Needs heat, reacts vigorously to produce solid Al2Cl6

Si reaction with chlorine gas

Needs heat, slow reaction to produce liquid SiCl4

P reaction with chlorine gas

Chlorine gas in excess, heat, slow reaction to form PCl5

Na reaction with cold water

Vigorous reaction, sodium melts into a ball of molten metal, moves across the surface of the water, quickly becoming smaller until it disappears, and fizzes as hydrogen gas is given off. NaOH solution is formed, of pH 14

Mg reaction with water

Reacts very slowly with cold water, to form a weakly alkaline solution of pH 11, since Mg(OH)2 is only slightly soluble. When magnesium is heated, it reacts vigorously with steam to form MgO and H2.

Oxidisation states of period 3 elements in their oxides oxides

Positive, as oxygen is more electronegative than the other period 3 elements

Na2O and water reaction

Forms NaOH, pH 14

MgO reaction with water

Forms Mg(OH)2, weakly alkaline, pH 10

Al2O3 reaction with water

No reaction!

SiO2 reaction with water

No reaction!

P4O10 reaction with water

Vigorous reaction, forms H3PO4, weakly acidic, pH 3-4

SO2 reaction with water

Forms H2SO3, strongly acidic, pH 1-2

SO3 reaction with water

Forms H2SO4, strongly acidic, pH 1-2

Acid/base reaction of Al2O3

Amphoteric - can react as an acid or a base. With sulfuric acid, forms Al2(SO4)3 and H2O. With sodium hydroxide, forms NaAl(OH)4

Acid/base reaction of SiO2

Reacts with NaOH to form Na2SiO3 and H2O

Acid/base reaction of P4O10

Forms Na3PO4 and H20

Acid/base reaction of SO2

Reacts with NaOH to form Na2SO3 an H2O

Acid/base reaction of SO3

Reacts with NaOH to form Na2SO4 and H2O

When is aluminium chloride a lattice and when is it a dimer

Hydrated, it is an AlCl3 ionic lattice. Without water, it exists as Al2Cl6 dimers.

NaCl and MgCl2 reactions with water

White solids dissolve to form colourless solutions. NaCl solution is pH 7 and MgCl2 solution is 6.5

Al2Cl6, SiCl4, PCl5 and SCl2 reactions with water

Chlorides react with water, giving off white fumes of HCl gas. Al2Cl6 pH 3, rest pH 2

Going across period 3, chlorides reaction with water

First, ionic chlorides which dissolve in water. Then, metallic chlorides which are hydrolysed by water to form an acid as one of the products. Then, simple molecular chlorides which hydrolyse to form acids when added to water.

Al2Cl6 reaction with water

• The dimers are broken down and Al3+ and Cl- ions are in solution

• Al3+ ions become hydrated (they are small and highly charged) and causes a water molecule bonded to it to lose an H+ ion - this turns the solution acidic

• Equation: [Al(H2O)6]3+ —> [Al(H20)5OH]2+ + H+ (all aq)

Reaction of SiCl4 with water

Hydrolysed by water, releasing white fumes of HCl gas and forming a white precipitate of SiO2 in a rapid reaction. (Some of the gaseous HCl dissolves in water to form hydrochloric acid.)

Reaction of PCl5 with water

Hydrolysed by water, forms aqueous phosphoric acid and gaseous HCl (white fumes) - highly acidic solution.