GROUP IV

element	atomin no	electronic config	nature
carbon, C	6	1s22s22p2	non-metal
silicon, Si	14	[Ne]3s23p2	metalloid
germanium, Ge	32	[Ar]3d104s24p2	metalloid
tin, Sn	50	[Kr]4d105s25p2	metal
lead, Pb	82	[Xe]4f145d106s26p2	metal

ns²np²: valence shell electron config
Variation in mp

C(diamond), Si: gaint covalent structures (diamond-like) > large amt of energy to break many cov bonds
Sn, Pb: giant metallic but outer valence electrons attracted less (large atomic radius & sheilding effect) > weaker metallic bonds

Variation in electrical conductivity
-increases down group
C(graphite): fairly good conductor- delocalised electrons present
Si, Ge: gaint covalent structures- semi-conductors > conduct elec under certain conditions
Sn, Pb: metals > many delocalised electrons present


Tetrachlorides, MCl₄
all form covalent tetrachlorides (oxidation state: +4) (tetrahedral molecule- sp³ hybridisation) w/ simple molecular structure
-volatile at room temp & pressure (non-polar molecules attracted by weak van der Waal's forces)


Hydrolysis of tetrachlorides
tetrachlorides, except CCl₄, hydrolysed to dioxide + HCl(g)



MCl₄(l) + 2H₂O > MO₂(s) + 4HCl(g)
during hydrolysis expansion of the octet is achieved by using empty d-orbitals to form dative bonds w/ water, replacing Cl atom one by one w/ -OH > M(OH)₄ > decomposes > MO(s)
(CCl₄: no reaction as no empty d-orbitals for dative bond formation w/ water molecule)
Group IV oxides
-monoxides(+2), dioxides(+4)
-Monoxides

oxide	structure	type of oxide	thermal stability
CO	simple molecular	metal oxide; no reaction w/ acid / alkali	readily oxidised to CO2
SiO	simple molecular	metal oxide; no reaction w/ acid / alkali	readily oxidised to SiO2 in air
GeO	predominantly ionic; giant ionic	amphoteric	readily oxidised to GeO2 in air
SnO	predominantly ionic; giant ionic	amphoteric	readily oxidised to SnO2 in air
PbO	predominantly ionic; giant ionic	amphoteric	stable to heat

carbon monoxide,CO
-colourless, poisonous gas
-netrual oxide, no reaction w/ acid/ alkali
-burns in air w/ pale blue flame > CO₂: CO(g) + O₂(g) > 2CO₂(g)

silicon(II) monoxide, SiO
-brown solid, exists at v.high temp only (O₂ can't react)
-neutral oxide, no reaction w/ acid/ alkali
-at rtp: oxidised by air > white silicon dioxide: 2SiO(s) + O₂(g) > 2SiO₂(s)

germanium(II) oxide
-anhydrous GeO- black solid insoluble in water
-amphoteric oxide, reacting slightly w/ acid & alkali
-readily oxidised to GeO₂ in air: 2GeO(s) + O₂(g) > 2GeO₂(s)
-heated at ~500°C in absence of air > disproportionates > GeO₂ & Ge: 2GeO(s) >(500°C, absence of air)> Ge(s) + GeO₂(s)

tin(II) oxide
-dark brown solid, insoluble in water
-spontaneously oxidised in air (exothermic reaction) > tin(IV) oxide: 2SnO(s) + O₂(g) > 2SnO₂(s)
-amphoteric oxides; + acid > Sn²⁺ ion, + alkali > hydroxostannate(II) ion, Sn(OH)₃^-(aq)
SnO(s) + 2H⁺(aq) > Sn²⁺(aq) + H₂O(l)
SnO(s) + OH^-(aq) + H₂O(l) > Sn(OH)₃^-(aq)

lead(II) oxide
-yellow solid, insoluble in water
-amphoteric oxide, + acids > Pb²⁺(aq), + alkali > hydroxoyplumbate(II) ion, Pb(OH)₃^-(aq)
PbO(s) + 2H⁺(aq) > Pb²⁺(aq) + H₂O(l)
PbO(s) + OH^-(aq) + H₂O(l) > Pb(OH)₃^-(aq)
-stable to heat

-Dioxides

oxide	structure	type of oxide	thermal stability
CO2	simple molecular	acidic	stable at high temp
SiO2	giant molecular	acidic	stable at high temp
GeO2	intermediate bet giant molecular & giant ionic	amphoteric	stable at high temp
SnO2	intermediate bet giant molecular & giant ionic	amphoteric	stable at high temp
PbO2	intermediate bet giant molecular & giant ionic	amphoteric	decomposes to PbO on heating

carbon dioxide, CO₂
-colouless gas, dissolves in water > dibasic carbonic acid: CO₂(g) + H₂O(l) > H₂CO₃(aq)
-acidic oxide, + alkali > salt carbonate: CO₂(g) + 2OH^-(aq) > CO₃^2-(aq) + H₂O(l)
-stable at high temp

silicon(IV) dioxide, SiO₂
-white solid, insoluble in water
-acidic oxide,+ alkali > silicates: SiO₂(s) + OH^-(aq) > SiO₃^2-(aq) + H₂O(l)

germanium(IV) oxide
-white solid
-amphoteric oxide, + conc acid > Ge⁴⁺(aq), + conc alkali > germanate(IV) salts
GeO₂(s) + 4H⁺(aq) > Ge⁴⁺(aq) + 2H₂O(l)
GeO₂(s) + 2OH^-(aq) > GeO₃^2-(aq) + H₂O(l)

tin(II) oxide
-white solid
-amphoteric oxides; + conc acid > Sn⁴⁺ ion, + conc alkali > stannate(II) ion
SnO₂(s) + 4H⁺(aq) > Sn⁴⁺(aq) + 2H₂O(l)
SnO₂(s) + 2OH^-(aq) > SnO₃^2-(aq) + H₂O(l)

lead(II) oxide
-dark brown solid
-amphoteric oxide, + conc acids > covalent 4+ salt, + conc alkali > plumbate(II) ion, PbO₃^2-(aq)
PbO₂(s) + 4HCl(aq) > PbCl₄(l) + 2H₂O(l)
PbO₂(s) + 2OH^-(aq) > PbO₃^2-(aq) + H₂O(l)
-PbO₂ decomposed on heating (~300°C) > PbO(s) + oxygen: 2PbO₂(s) >(heat, 300°C)> 2PbO(s) + O₂(g) [dark brown solid > yellow solid]

Relative stability of +4 & +2 oxidation state
down group IV stability of: +4 state decreases, +2 state increases
-due to inert pair effect: increasing tendency for the 2 s-electrons not to take part in bonding as atomic size increases down the group, the 2 p-electrons are held less tightly (atomic size & shielding increases) > easily lost > +2 ion
C, Si: +4- v.stable relative to +2, +2 state;
CO: rare & easily oxidised to +4 (v.exothermic): 2CO(g) + O₂(g) > 2CO₂ (g), ΔH= -283kJ/mol
SiO₂: unstable in normal conditions
Ge: GeO & GeO₂ exists but GeO, a reducing agent, readily oxidised in air (or when heat) > GeO₂
Sn:+4 state only slightly more stable
Sn²⁺(aq): mild reducing agent- reduces iodine to iodide: Sn²⁺(aq) + I₂(s) > Sn⁴⁺(aq) + 2I^-(aq)
Pb: Pb²⁺ more stable than Pb⁴⁺, PbO₂- strong oxidising agent, oxidises conc HCl to chlorine: PbO₂(s) + 4HCl(aq) > PbCl₂(s) + Cl₂ (g) + 2H₂O(l)

greater stability of +2 state down group IV show by standard electrode potential, of M⁴⁺(aq)/M²⁺(aq) system of Ge, Sn & Pb
Ge⁴⁺(aq) + 2e^- Ge²⁺(aq), = -1.6V
Sn⁴⁺(aq) + 2e^- Sn²⁺(aq), = +0.15V
Pb⁴⁺(aq) + 2e^- Pb²⁺(aq), = +1.8V
: more +ve from Ge⁴⁺ to Pb⁴⁺ > +4 state more easily reduced to +2 state

Uses of group IV elements
C: diamonds- jewellery, tips of drilling parts, graphite- carbon fibres (turbine blades, racing car brakes, hulls of speed boats), lubricant at hihg temp, pencil 'leads', inert electrodes, moderator in nuclear reactors
Si: semi-conductor in silicon chips in electronic circuits, component in glass (glass- calcium silicate & sodium silicate), silicones (silicon-based polymers- in plastic & cosmetic surgery), ceramics (mixture of silica & silicates used in engine parts & temp resistant furniture)
Ge: semi-conductor, less widely used than Si
Sn: surface layer to protect Fe & stell objects (resistant to acids)
Pb: electrodes in car batteries, screen against radiation, solder (alloy of Pb & Sn)
Ceramics
-made from materials w/ giant ionic structures (Al₂O₃) & giant covalent structure (SiO₂) > strong ionic bonds & vast covalent bonds > v. heat resistant (refractories), resistant to chemicals, good electrical insulators (mp so high > doesn't melt > can't conduct)
Uses: engine parts, furnaces, crucibles for molten metals, insulators for elec c