Chem5 - Periodicity

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First Ionisation Energy - The energy required to remove one mole of outer electrons from one mole of gaseous atoms.
( Mɽɡɿ → M+ɽɡɿ + e- )

Atomic Radius - The distance between the nucleus to the outer electrons.

Electronegativity - The power of an atom to attract electron density from a covalent bond. (i.e. the more electronegative something is, the stronger it attracts.

Disproportionation - When oxidation and reduction occur at the same time with the same element.
( Cl2 + H2O ↔ HCl + HClO )

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Reactions with Water/Steam:


Fizzing/smoke: H2 gas is produced.
Pink trail is left in the water: OH- ions produced.
Na melts: exothermic reaction.

Mg(s) + H2O(l)
 → MgO(s) + H2(g)

Flame ignited at hole in test tube: H2 burning.
White powder formed: MgO produced.
Mg burned brightly: exothermic reaction. 

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Periodicity - Reactions with Oxygen

Na burns brightly with a yellow/orange flame producing white Na2O. Giant ionic lattice structure with ionic bonding due to the large electronegative difference. It has a high melting point of 1275c due to strong electrostatic forces between ions which require lots of energy.

Mg burns with a bright white flame producing white MgO. Giant ionic lattice with ionic bonding. It has a higher melting point of 2852c than Na2O as Mg2+ is smaller, doubly charged and has a greater charge density. MgO has stronger electrostatic attractions

Al burns with a bright white flame producing white Al2O3. Giant ionic lattice with ionic bonding and some covalent character due to smaller electronegativity difference. Has a high melting point of 2072c which is greater than Na2O due to strong electrostatic attractions but less than MgO due to the 2:3 ratio of ions.

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Periodicity - Reactions with Oxygen

Si(s) + O2(g) → SiO2(s)
Si burns with a bright white flame to produce white silicon dioxide. Macromolecular/Giant covalent structure with many covalent bonds. SiO2 has a high melting point (1610c) due to many strong covalent bonds which require a high amount of energy to break.

4P(s) + 5O2(g) → P4O10(s)

White P ignites in air, burning with a white flame. White smoke of P4O10 is produced. Simple molecular structure with covalent bonding. Melting point low as Van der Waals forces need to be overcome which are weak.

S(yellow powder) burns with blue flame producing colourless SO2, small amts of SO3. Simple molecular, covalent bonding, Van der Waals forces and dipole attractions, melting point low (-73c) as little energy needed.

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Periodicity - Reactions of Oxides

Metal Oxides are ionic: the electronegativity difference is large.

Na2O(s) + H2O(l) → 2NaOH(aq)        (Strong alkali - fully diss. into
pH = 13-14                                                       Na+ and OH-)

Na2O + 2HCl → 2NaCl + H2O
Na2O + 2HNO3 → 2NaNO3 + H2O              (O2- + 2H+ → H2O)
Na2O + H2SO4 → Na2SO4 + H2O

MgO(s) + H2O(l) → Mg(OH)2     (Weak alkali - slightly diss. into
pH = 9-10                             Mg2+ and OH- as not very soluble)
MgO + 2HCl → MgCl2 + H2O
MgO + 2HNO3 → Mg(NO3)2 + H2O              (O2- + 2H+ → H2O)
MgO + H2SO4 → MgSO4 + H2O

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Periodicity - Reactions of Oxides


pH = 7, basic oxide
Al2O3 + 6HCl → 2AlCl3 + 3H2O 
Al2O3 + 6HNO
→ 2Al(NO3)3 + 3H2O 
Al2O3 + 3H2SO
 Al2(SO4)3 + 3H2O
Al2O3 + 2NaOH + 3H2
→ 2[Al(OH)4]- 

pH = 7, acidic oxide 
SiO2(s) + 2NaOH(aq) → NaSiO3(s) + H2O(l)

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Periodicity - Reactions of Oxides

P4O10 + 6H2O → 4H3PO4
(strong acid, pH = 0-1)
P4O10 + 12NaOH → 4Na3PO4 + 6H2O
H3PO4 + NaOH → NaH2PO4 + H2O
NaH2PO4 + NaOH → Na2HPO4 + H2O
Na2HPO4 + NaOH → Na3PO4 + H2O
Overall: H3PO4 + 3NaOH → Na3PO4 + 3H2O

SO2 + H2O → H2SO3
(weak acid, pH = 2-3)
H2SO3 + NaOH → NaHSO3 + H2O
NaHSO3 + NaOH → Na2SO3 + H2O
Overall: H2SO3 + 2NaOH → Na2SO3 + 2H2O
SO2(g) + CaO(s) → CaSO3(s)
SO3 + H2O → H2SO4
H2SO4 + 2NaOH → Na2SO4 + 2H2O
SO3 + 2NaOH → Na2SO4 + H2O

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