Elements that have similar chemical properties are found in the same group of periodic table. Group 4 elements occurs within the p block of the periodic table. Group 4 contains non-metallic, metalloid and metallic elements.
Trends in group 4
Group 4 consists of 5 elements carbon, silicon, germanium, tin and lead and is situated at the center of the periodic table. The general outer electron structure for this group of element is ns2np2.
There is the following trend as the group is descended:
- An increase in the size of the atoms and the density of the elements
- A decrease in the melting point and boiling point, electronegativity and first ionization energy
- A change in structure of elements from giant molecular lattice in carbon, silicon and germanium to giant metallic lattice in tin and lead.
Carbon, silicon and germanium
The lighter elements, carbon and silicon are non-metallic.
Tin and lead
The heavier elements of group 4, tin and lead are predominantly metallic. Both tin and lead are heavily used as alloy metals.
Compounds of group 4 elements
Reaction with oxygen
Carbon, silicon, germanium and tin are all unaffected by air at room temperature but they burn when strongly heated in air.
C(s) + O2 (g) → CO2
Sn(s) + O2 (g) → SnO2(s)
2Pb(s) + O2 (g) → 2PbO(s)
The oxides formed are thus acidic.
Similarly, germinates are formed by an acid-base reaction.
GeO2(s) + Na2O (s) → Na2GeO3 (s)
The oxides of tin and lead are both amphoteric and therefore can react with both acid and base.
SnO2 + 6HCl (aq) → [SnCl6] (aq) + 2H3O+
PbO(s) + 2HCl (aq) → PbCl2 (s) + H2O (l)
Reaction with Chlorine
Carbon, silicon, germanium and tin all react with chlorine to form chloride
Si(s) + 2Cl2(g) → SiCl (l)
Ge(s) + 2Cl2(g) → GeCl4 (l)
The reaction between carbon and chlorine is slow. Hence CCl4 is usually manufactured.
CS2 (l) + 3Cl2(g) → CCl4 (l) + S2Cl2 (l)
Pb2+ (aq) + 2Cl– (aq) → PbCl2 (s)