Period 3
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Trend in atomic radius across period 3
• increase in nuclear charge • same shielding • decrease in atomic radius
Trend in electronegativity across period 3
• increase in nuclear charge • same shielding • elements more capable of withdrawing electron density from covalent bond
Trend in 1st ionisation energy across period 3
• increase in nuclear charge • same shielding • greater attraction between outer electrons and positive nucleus • requires more energy to be removed
Why does Al have a lower 1st IE than Mg?
• Al electron removed from 3p sub shell • Mg electron removed from 3s sub shell • 3p higher in energy than 3s • so less energy required to remove electron
Why does S have lower 1st IE than P?
• S electron removed from 3p paired orbital • P electron removed from 3p unpaired orbital • S has lower 1st IE due to electron pair repulsion
Why does melting point increase from Na to Al?
• charge of metal ion increases • size of metal ion decreases • increase in strength of attraction between metal ions and delocalised electrons
Why does silicon have the highest melting point?
• Macromolecular • with strong covalent bonds • more energy needed to overcome
Why does S8 have higher MP/BP than P4?
• s8 bigger molecule • stronger VDW
Why does P4 have higher MP/BP than Cl2?
• P4 bigger molecule • stronger VDW
Why does Cl2 have higher MP/BP than Ar?
• Cl2 bigger molecule • stronger VDW • Ar only one atom - weaker VDW
Why does Al have the highest boiling point?
• once Si melted only a little more energy needed to overcome strong covalent bonds • Al has strong electrostatic forces of attraction between positive ions and delocalised electrons in liquid state
Reaction of Na with cold water and pH
Na (s) + H2O (l) —> NaOH (aq) + H2 (g) pH 13-14
What happens when Na reacts with cold water?
• effervescence • metal melts • strong alkali solution formed
Reaction of Mg with cold water and pH
Mg (s) + H2O (l) —> Mg(OH)2 (aq) + H2 pH 9-10
What happens when Mg reacts with cold water?
• slow reaction at room temp • few bubbles of gas produced • weak alkali formed • as Mg(OH)2 sparingly soluble
Reaction of Mg with steam
Mg (s) + H2O (g) —>. MgO (s) + H2 (g)
2 reactions of Cl with cold water and pH
Reaction 1: Cl2 (g) + H2O (l) —> HClO (aq) + HCl (aq) Reaction 2: Cl2 (g) + H2O (l) —> 4HCl (aq) + O2 (g) Both pH 2-3
Silicon(IV) oxide is insoluble in water. Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide.
• Reacts with alkalis • SiO2 + 2NaOH —> Na2SiO3 + H2O
Explain why Mg has higher MP than Na+
• Mg2+ has greater charge than Na+ • stronger electrostatic forces of attraction between Mg2+ and delocalised electrons
State structure and bonding of silicon dioxide. Give 2 physical properties apart from high MP
Structure: Macromolecular Bonding: Covalent Physical properties: Hard/brittle/non-conductor/insoluble
Give the formula of the species in a sample of solid phosphorus(V) oxide. State the structure of, and describe fully the bonding in, this oxide.
Formula: P4 O10 Structure: simple molecular Bonding: covalent and VDW between molecules
Sulfur(IV) oxide reacts with water to form a solution containing ions. Write an equation for this reaction
SO2 + H2O → 2H+ + SO3 2- OR SO2 + H2O → H+ + HSO3 -
Write an equation for the reaction between the acidic oxide, phosphorus(V) oxide, and the basic oxide, magnesium oxide.
P4O10 + 6MgO → 2Mg3(PO4)2 OR P4O10 + 6MgO → 6Mg2+ + 4PO43-
State the type of bonding in magnesium oxide. Outline a simple experiment to demonstrate that magnesium oxide has this type of bonding.
• MgO is ionic • melt it • molten oxides conduct electricity