2.4: Properties of Period 3 elements and their oxides

What is the equation for the reaction of Na with water?

2Na + 2H₂O → 2NaOH + H₂

What is the equation for the reaction of Mg with water?

Mg + 2H₂O → Mg(OH)₂ + H₂

Explain which is more reactive with water, Na or Mg?

• Na is more reactive

• Only has to lose 1 electon, whereas Mg needs to lose 2 electrons

• So less energy is required

How can the rate of reaction for Mg and water be increased, and why?

• The reaction is originally very slow

• Using steam instead of water

• As steam provides reaction with greater energy

What is the equation for the reaction of Mg with steam?

Mg + H₂O(g) → MgO(s) + H₂

What is the observation of the reaction of Mg and steam?

Bright white flame

What are the formulas names and oxidation states for the oxides that form from the period 3 elements?

What is the reaction of Na and O₂, what are the reaction conditions, observations and product?

• 4Na(s) + O₂(g) → 2Na₂O(s)

• Heated

• Bright yellow flame

• White solid

What is the reaction of Mg and O₂, what are the reaction conditions, observations and product?

• 2Mg(s) + O₂(g) → 2MgO(s)

• Heated

• Bright white flame

• White solid

What is the reaction of Al and O₂, what are the reaction conditions, observations and product?

• 4Al(s) + 3O₂(g) → 2Al₂O₃(s)

• Heated

• Bright white flame

• White powder

What is the reaction of Si and O₂, what are the reaction conditions, observations and product?

• Si(s) + O₂(g) → 2SiO₂(s)

• Powdered Si, heat strongly

• Bright white sparkles

• White powder

What is the reaction of P and O₂, what are the reaction conditions, observations and product?

• 4Ps) + 5O₂(g) → 2P₄O₁₀(s)

• Heated

• White/yellow flame

• White clouds

What is the reaction of S and O₂?

• S(s) + O₂(g) → 2SO₂(s)

• 2S(s) + 3O₂(g) → 2SO₃(g) (only with a catalyst and very high temperature)

• Powdered S, heated

• Blue flame

• Toxic fumes

What is the trend of the melting point of period 3 oxides?

• Increases and then rapidly decreases

• Na₂O: ionic

• MgO: ionic

• Al₂O₃: ionic but shows covalent character, so much lower than MgO

• SiO₂: macromolecular

• P₄O₁₀: simple covalent

• SO₂: simple covalent

The reactions of the oxides of the elements Na–S with water, limited to Na₂ O, MgO, Al₂ O₃ , SiO₂ , P₄ O₁₀ , SO₂ and SO₃ , and the pH of the solutions formed.

What is the equation of Na₂O with water, and what is the approximate pH of the solution formed?

• Na₂O(s) + H₂O(l) → 2NaOH(aq)

• 14

What is the equation of MgO with water, and what is the approximate pH of the solution formed?

• MgO (s) + H₂O (l) → Mg(OH)₂ (aq) 

• 10

What is the equation of Al₂O₃ with water, and what is the approximate pH of the solution formed?

No reaction, as Al₂O₃ is insoluble in water

What is the equation of SiO₂ with water, and what is the approximate pH of the solution formed?

No reaction, as SiO₂ is insoluble in water

What is the equation of P₄10 with water, and what is the approximate pH of the solution formed?

• P₄O₁₀ (s) + 6H₂O (l) → 4H₃PO₄ (aq)

• 2

What is the equation of SO₂ with water, and what is the approximate pH of the solution formed?

• SO₂ (g) + H₂O (l) → H₂SO₃ (aq)

• 2-3

What is the equation of SO₃ with water, and what is the approximate pH of the solution formed?

• SO₃ (g) + H₂O (l) → H₂SO₄ (aq)

• 0-1

What is the definition of amphoteric?

Compounds that act as both an acid and a base

What is the equation for the reaction of Na₂O and HCl?

Na₂O (s) + 2HCl (aq) → 2NaCl (aq) + H₂O (l)

What is the equation for the reaction of MgO and HCl?

MgO (s) + 2HCl (aq) → MgCl₂ (aq) + H₂O (l)

What are the equations for the reaction of Al₂O₃ reacting with H₂SO₄/NaOH?

• Al₂O₃ (s) + 3H₂SO₄ (aq) → Al₂(SO₄)₃ (aq) + 3H₂O (l)

• Al₂O₃ (s) + 2NaOH (aq) + 3H₂O (l) → 2NaAl(OH)₄ (aq)

What is the equation for the reaction of SiO₂ and NaOH?

SiO₂ (s) + 2NaOH (aq) → Na₂SiO₃ (aq) + H₂O (l)

What is the equation for the reaction of P₄O₁₀ and NaOH?

P₄O₁₀ (s) + 12NaOH → 4Na₃PO₄ + 6H₂O (l)

What are the equations for the reactions of SO₂/SO₃ with NaOH

• SO₂ (g) + 2NaOH (aq) → Na₂SO₃ (aq) + H₂O (l)

• SO₃ (g) + 2NaOH (aq) → Na₂SO₄ (aq) + H₂O (l)