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Back to AI Flashcard MakerChemistry /A-level Chemistry: 3.2.4 Properties of Period 3 Elements Part 1

A-level Chemistry: 3.2.4 Properties of Period 3 Elements Part 1

Chemistry38 CardsCreated 2 months ago

This flashcard set compares the reactivity of sodium and magnesium, explaining why sodium is more reactive and how each metal behaves when reacting with cold water. It includes observations, explanations, and relevant chemical equations.

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Explain why sodium is more reactive than magnesium

  • ∵ it takes less energy to lose 1 electron than to lose 2

  • ∴ more energy (usually heat) is needed for magnesium to react

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Key Terms

Term
Definition

Explain why sodium is more reactive than magnesium

  • ∵ it takes less energy to lose 1 electron than to lose 2

  • ∴ more energy (usually heat) is needed for magnesium to react

Sodium is more reactive than magnesium and this is shown in their reactions with ___

water

Describe how sodium reacts with cold water

  • Reacts vigorously

  • Forms molten ball on surface

  • Fizzing

    • Produces H2 gas

Write the equation for when sodium reacts with water

2Na + 2H₂O → 2NaOH + H₂↑

Describe how magnesium react with cold water

  • Reacts very slowly

  • Forms weakly alkaline solution

  • Forms thin coating of magnesium hydroxide forms on surface ...

Why is the solution produced from when magnesium reacts with cold water weakly alkaline?

  • ∵ magnesium hydroxide is not very soluble in water as its lattice is stronger

    • it’s sparingly soluble

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A-level Chemistry: 3.2.4 Properties of Period 3 Elements Part 1
TermDefinition

Explain why sodium is more reactive than magnesium

  • ∵ it takes less energy to lose 1 electron than to lose 2

  • ∴ more energy (usually heat) is needed for magnesium to react

Sodium is more reactive than magnesium and this is shown in their reactions with ___

water

Describe how sodium reacts with cold water

  • Reacts vigorously

  • Forms molten ball on surface

  • Fizzing

    • Produces H2 gas

Write the equation for when sodium reacts with water

2Na + 2H₂O → 2NaOH + H₂↑

Describe how magnesium react with cold water

  • Reacts very slowly

  • Forms weakly alkaline solution

  • Forms thin coating of magnesium hydroxide forms on surface of the metal

Why is the solution produced from when magnesium reacts with cold water weakly alkaline?

  • ∵ magnesium hydroxide is not very soluble in water as its lattice is stronger

    • it’s sparingly soluble

  • ∴ few hydroxide ions are produced

State the equation for when magnesium reacts with cold water

Mg + 2H₂O → Mg(OH)₂ + H₂↑

Describe how magnesium reacts with steam

  • Magnesium reacts faster with steam (i.e. when there’s more energy)

  • To form magnesium oxide

State the equation for when magnesium reacts with steam

Mg + H₂O (steam) → MgO + H₂↑

When Period 3 elements react with oxygen, what do they form?

oxides

When Period 3 elements react with oxygen, they are usually oxidised to their _____ oxidation states, same as their _____ _____

When Period 3 elements react with oxygen, they are usually oxidised to their highest oxidation states, same as their group numbers

Reactions with Oxygen

State which Period 3 element isn’t oxidised to their highest oxidation state & state its oxidation state

  • Sulfur forms SO₂

  • +4 oxidation state

Reactions with Oxygen

Explain why sulfur isn’t oxidised to its highest oxidation state

A high temp. and catalyst is needed to make SO3, where S has oxidation state of +6

More ____ metals (Na, Mg) and _____ (P, S) react readily in air, while ___ and ___ react slowly

More reactive metals (Na, Mg) and non-metals (P, S) react readily in air, while Al and Si react slowly

Na2O, MgO & Al2O3 have ____ melting points

high

Explain why Na2O, MgO & Al2O3 have high melting points

  • Giant ionic lattices

  • Strong forces of attraction between ions = lots of energy needed to break bonds

MgO has a ____ melting point than Na2O

higher

Why does MgO have a higher melting point than Na2O?


  • Mg forms 2+ ions

  • So bonds more strongly than 1+ Na ions in Na2O

Al2O3 has a ____ melting point than MgO


lower

Why does Al2O3 have a lower melting point than MgO?

  • ∵ of difference in electronegativity between Al and O isn’t as large as between Mg and O

  • Means oxygen ions in Al2O3 don’t attract electrons in metal-oxygen bond as strongly MgO

  • Makes bonds in Al2O3 partially covalent

SiO2 has a _____ melting point than non-metal oxides


higher

Why does SiO2 have a higher melting point than non-metal oxides

  • ∵ has giant macromolecular structure

  • Have to break strong covalent bonds = lots of energy

Why does P4O10 and SO2 have low melting points?

  • ∵ form simple molecular structure

  • Have weak intermolecular forces (dipole-dipole and van der Waals)

  • Take little energy to break

State the equation for when sodium and oxygen react, include state symbols

4Na (s)+O2​(g)→2Na2​O (s)
(Sodium reacts with oxygen to form sodium oxide.)

State the equation for when aluminium and oxygen react, include state symbols


4Al (s)+3O2​(g)→2Al2​O3​(s)
(Aluminium reacts with oxygen to form aluminium oxide.)

State the equation for when phosphorus and oxygen react, include state symbols.


4P (s)+5O2​(g)→2P2​O5​(s)
(White phosphorus reacts with oxygen to form diphosphorus pentoxide.)

State the equation for when magnesium and oxygen react, include state symbols

2Mg (s)+O2​(g)→2MgO (s)
(Magnesium reacts with oxygen to form magnesium oxide.)

State the equation for when silicon and oxygen react, include state symbols

Si (s)+O2​(g)→SiO2​(s)
(Silicon reacts with oxygen to form silicon dioxide.)

State the equation for when sulfur and oxygen react, include state symbols

S (s)+O2​(g)→SO2​(g)
(Sulfur reacts with oxygen to form sulfur dioxide.)

Ionic Oxides are _____

Alkaline

Covalent Oxides are ____

Acidic

Explain why ionic oxides are alkaline

  • Ionic oxides (of Na and Mg) contain oxide ions (O2-)

  • When they dissolve in water, O2- ions accept protons from water molecules to form hydroxide ions

Explain why the ionic oxides of Na are more alkaline than those for Mg

Sodium hydroxide is more soluble in water ∴ more alkaline solution than magnesium hydroxide

State the equation for when sodium oxide reacts with water and include rough pH of solution formed

Na₂O + H₂O → 2NaOH
pH ≈ 13–14

State the equation for when magnesium oxide reacts with water and include rough pH of solution formed

MgO + H₂O → Mg(OH)₂
pH ≈ 9–10

Explain why covalent oxides (e.g. oxides of phosphorus and sulfur) are acidic

They dissociate in solution forming hydrogen ions and negative ion (called conjugate base)

Simple covalent oxides of non-metals phosphorus and sulfur form acidic solutions that are ___ so the pH is around ___

Simple covalent oxides of non-metals phosphorus and sulfur form acidic solutions that are strong so the pH is around 0-2 (for at least 1 mol dm-3)

State the equation for when phosphorus(V) oxide reacts with water. Include pH.

P₄O₁₀ + 6H₂O → 4H₃PO₄
pH ≈ 0