5.1.1 and 5.1.2: Period 3 elements and oxides Flashcards
Where is period 3
third row in periodic table
Elements in period 3
(don’t need to know 100% but good to know ish)
8
sodium magnesium aluminium silicon phosphorus sulphur chlorine argon
Which more reactive and why
sodium vs magnesium
Sodium is more reactive because it takes less energy to lose one electron than two, so more energy is needed for Mg to react. (as Na is in group 1, Mg is in group 2)
Reaction of sodium with cold water
vigorous reaction, forms a molten ball on the surface of the water, fizzes and produces H2 gas
Reaction of sodium with cold water
equation
2Na + 2H2O > 2NaOH + H2
pH of solution formed from reaction of sodium with cold water
pH 12-14
NaOH produced - strongly alkaline
Reaction of magnesium with cold water
equation
Mg + 2H2O > Mg(OH)2 + H2
Reaction of magnesium with cold water
Reacts very slowly
no visible reaction
pH of solution formed from reaction of magnesium with cold water
and why
weakly alkaline solution
pH 9-10
because magnesium hydroxide is not very soluble in water
Reaction of magnesium with steam
much faster reaction than with cold water
Reaction of magnesium with steam
equation
Mg + H2O > MgO + H2
Overall word equation for reactions of period 3 elements to form oxides
element + oxygen > oxide
Which oxidation state are elements usually oxidised to when they react with oxygen
Exception to this?
Highest oxidation state (same as their group numbers)
Exception: sulphur, +6 oxidation state but forms SO2 in which its oxidation state is +4
Equations for oxidation of sodium, magnesium and aluminium
2Na + 0.5O2 > Na2O
Mg + 0.5O2 > MgO
2Al + 1.5O2 > Al2O3
Equations for oxidation of silicon, phosphorus and sulphur
Si + O2 > SiO2
P4 + 5O2 > P4O10
S + O2 > SO2
Reaction speeds of oxides of sodium and magnesium in air
and flame colour
Na2O: vigorous, yellow flame
MgO: vigorous, brilliant white flame
Reaction speeds of oxides of aluminium and silicon in air
and flame colour
Al2O3 and SiO2: slow, no flame colour
Reaction speeds of oxides of phosphorus and sulphur in air
and flame colour
P4O10: spontaneously combusts, brilliant white flame
SO2: burns steadily, blue flame
Trend in melting points across period 3
increase, from Na2O to MgO
decrease from MgO to SO3
Crystal structures of period 3 oxides?
Na2O, MgO, Al2O3: giant ionic lattices
SiO2: giant covalent
P4O10, SO2: simple covalent
Equation for reaction of sodium oxide with water
and pH of solution formed
Na2O + H2O > 2NaOH
pH: 12-14
Equation for reaction of magnesium oxide with water
and pH of solution formed
MgO + H2O > Mg(OH)2
pH: 9-10
Equation for reaction of phosphorus oxide with water
and acid formed
p4O10 + 6H2O > 4H3PO4
phosphoric (V) acid
Equation for reaction of sulphur dioxide with water
and acid formed
SO2 + H2O > H2SO3
sulphuric (IV) acid
Equation for reaction of sulphur trioxide with water
and acid formed
SO3 + H2O > H2SO4
sulphuric (VI) acid
Reactions of Al2O3 and SiO2 with water
no reactions!!
both insoluble in water
Why don’t Al2O3 and SiO2 react with water
SiO2: giant covalent so insoluble in water
Al2O3: partially ionic and partially covalent so insoluble in water
Amphoteric
Will react with an acid or a base
Acid neutralisation reaction
acid and base = salt and water
Which period 3 oxides react with acids
(to neutralise them)
why?
sodium and magnesium oxides
because they’re basic
Which period 3 oxides react with bases
(to neutralise them)
why?
silicon, phosphorus and sulphur oxides
because they’re acidic
Which period 3 oxide will react with acids or bases
(to neutralise them)
why?
Aluminium oxide
because its amphoteric
