8.1 - 8.4 + 22.1 - 22.3 Periodicity Flashcards
What structure and bonding do each of the elements in period 3 have?
Na, Mg, Al - Giant metallic
Si - Giant covalent
P, S, Cl - Simple molecular
Ar - Simple atomic
Explain the melting points across period 3
Increases Na to Al:
- Charge on positive ion and the number of delocalised electrons increases
- So metallic bond gets stronger
Si has the highest:
- Macromolecular structure has lots of strong covalent bonds to break
Decrease P to Ar:
- M.p determined by the size of Van der Waals forces
- S8 > P4 > Cl2 > Ar
Explain the trend in atomic radius across period 3
Decreases across period because:
- Nuclear charge increases but no. of energy levels stays the same
- This means atomic radius gets smaller
Explain the trend in first ionisation energy across period 3
Generally increases across period because:
- Nuclear charge increases but shielding stays the same
Exceptions:
- Decrease Mg to Al because Al outer electron is further away and more shielded in 3p orbital
- Decrease P to S because S has an electron pair repelling each other
Describe the reaction of sodium (Na) with oxygen
- Burns vigorously; yellow flame
- Very hot
4Na + O₂ → 2Na₂O
Describe the reaction of magnesium (Mg) with oxygen
- Burns vigorously; white flame
- Ash formed
2Mg + O₂ → 2MgO
Describe the reaction of aluminium (Al) with oxygen
- Burns vigorously
- Often has protective oxide layer
- White flame
4Al + 3O₂ → 2Al₂O₃
Describe the reaction of silicon (Si) with oxygen
- Slow reaction that requires heat
Si + O₂ → SiO₂
Describe the reaction of phosphorus (P) with oxygen
- Red phosphorous must be heated
- White phosphorous reacts spontaneously
P₄ + 5O₂ → P₄O₁₀
Describe the reaction of sulfur (S) with oxygen
- Melts easily
- Produces a pungent choking gas
- Burns with a blue flame
S + O₂ → SO₂
2S + 3O₂ → 2SO₃
Describe the reaction of sodium (Na) with water
- Reacts vigorously
- Fizzes rapidly
- Floats
- Melts due to heat
- Forms strongly alkaline solution
2Na + 2H₂O → 2NaOH + H₂
Describe the reaction of magnesium (Mg) with water
- Reacts slowly
- Sparingly soluble
- Forms weakly alkaline solution
Mg + 2H₂O → Mg(OH)₂ + H₂
Describe the reaction of magnesium (Mg) with steam
- More vigorous
- White light
Mg + H₂O → MgO + H₂
Describe the reaction of sodium oxide (Na₂O) with water
- Dissolves exothermically
- Solution formed = pH 13
- Oxide ion reacts with water and gains a H
Na₂O + H₂O → 2NaOH
Describe the reaction of magnesium oxide (MgO) with water
- Sparingly soluble
- Solution formed = pH 9
MgO + H₂O → Mg(OH)₂
Describe the reaction of aluminium oxide (Al₂O₃) with water
- Insoluble
- Solution formed = pH 7
Describe the reaction of silicon oxide (SiO₂) with water
- Insoluble
- Solution formed = pH 7
Describe the reaction of phosphorus oxide (P₄O₁₀) with water
- Soluble
- Solution formed = pH 1
- P₄O₁₀ disosciates fully and is triporotic so [H⁺] is increased and therefore the pH decreases
P₄O₁₀ + 6H₂O → 4H₃PO₄
Describe the reaction of sulphur dioxide (SO₂) with water
- Reasonably soluble
- Solution formed = pH 3
SO₂ + H₂O → H₂SO₃
Describe the reaction of sulphur trioxide (SO₃) with water
- Soluble
- Violent reaction
- Solution formed = pH 0
SO₃ + H₂O → H₂SO₄
What is the acidic/base nature of basic metal oxides?
Will react with acids
Describe the reaction between sodium oxide and sulphuric acid
Na₂O + H₂SO₄ → Na₂SO₄ + H₂O
Describe the reaction of magnesium oxide (MgO) and sulphuric acid
MgO + H₂SO₄ → MgSO₄ + H₂O
What is the acidic/base nature of amphoteric metal oxides?
Will react with acids and bases
Describe the reaction of aluminium oxide and HCl
Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Al2O3 + 6H+ → 2Al3+ + 3H2O
Describe the reaction of aluminium oxide and sodium hydroxide
Al₂O₃ + 2NaOH → 2NaAl(OH)₄ + 3H₂O
Al2O3 + 2OH− → 2Al(OH) +3H2O
What is the acidic/base nature of non-metal oxides?
Will react with bases
Describe the reaction of the non-metal oxide silicon oxide (SiO₂) and sodium hydroxide
- SiO₂ acts as a weak acid with strong bases
SiO₂ + 2NaOH → 2Na₂SiO₃ + H₂O
Phosphorus oxide (P₄O₁₀) becomes phosphoric acid (H₃PO₄) when dissolved in water. Describe the reaction of H₃PO₄ with sodium hydroxide.
Loses 3 protons so the reaction occurs in 3 stages:
H₃PO₄ + NaOH → NaH₂PO₄ + H₂O
NaH₂PO₄ + NaOH → Na₂HPO₄ + H₂O
Na₂HPO₄ + NaOH → Na₃PO₄ + H₂O
Overall:
H₃PO₄ + 3NaOH → Na₃PO₄ + 3H₂O
or
P4O10 + 12NaOH → 4Na3PO4 + 6H2O
Describe the reaction of the non-metal oxide sulphur dioxide (SO₂) and sodium hydroxide
SO₂ + NaOH → NaHSO₃
and then…
NaHSO₃ + NaOH → Na₂SO₃ + H₂O
Describe the structure of the period 3 oxides
Na20, MgO, Al2O3 = Ionic
SiO2 = Macromolecular
P4O6, P4O10, SO2, SO3, Cl2O, Cl2O7 = Simple molecular
What type of bonding do period 3 oxides Na -> Al have?
- Ionic
- Contain 02- ions
- O2- ions accept protons to form OH-
What type of bonding is present in Aluminium oxide (Al₂O₃)?
Ionic
Explain why the Van der Waals forces in liquid argon are very weak
- Argon particles are single atoms with electrons closer to the nucleus
- Cannot easily be polarised
