Chemistry of Carbon Compounds

Chemistry of Group 14 Elements

• Group 14 elements include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb)
• A gradation exists from non-metallic carbon to the predominantly metallic lead
• Carbon is a vital component of life, forming both organic and inorganic compounds
• Silicon is crucial in modern technology, particularly electronics and construction
• Silicon and germanium are classified as semi-metals, exhibiting both metallic and non-metallic properties
• Tin and lead have been used since antiquity
• These elements have varying electronic configurations, with the most general outer shell configuration being ns2np2

Electronic Structure of Group 14 Elements

• Carbon (6C): [He] 2s2 2p2
• Silicon (14Si): [Ne] 3s2 3p2
• Germanium (32Ge): [Ar] 3d10 4s2 4p2
• Tin (50Sn): [Kr] 4d10 5s2 5p2
• Lead (52Pb): [Xe] 4f14 5d10 6s2 6p2

General Properties of Group 14 Elements

• Atomic and Ionic Sizes: Atomic and ionic sizes decrease from C to Si, increase down the group from C to Pb.
• Ionization Energy: First ionization energy is generally higher for Group 14 compared to Group 13 elements, but decreases down the group, except for lead.
• Metallic and Nonmetallic Character: Metallic character increases as you move down the group; carbon and silicon are nonmetals, germanium is a metalloid, tin and lead are metals
• Oxidation States: The most common oxidation state is +4, but the +2 state becomes more stable down the group.
• Nature of Compounds: Most group 14 compounds are tetravalent, with covalent bonding being dominant.

Anomalous Behavior of Carbon

• Carbon differs significantly from other Group 14 elements due to its small size, high ionization energy, and high electronegativity.
• It can form pπ–pπ multiple bonds
• It has a strong propensity for catenation (forming chains and rings of identical atoms)
• Forms a wide variety of compounds, unlike other Group 14 elements

Properties of Carbon: Diamond and Graphite

• Diamond: Hardest natural substance; sp³ hybridized carbon atoms; high melting point; poor electrical conductivity
• Graphite: Good electrical conductor; sp² hybridized carbon atoms; layered structure; very soft; high melting point; important lubricating material

Occurrence of Group 14 Elements

• Abundant occurrence of carbon in various forms.
• Silicon is a major component of the Earth's crust.

Properties and Uses of Silicon

• Hard and brittle solid.
• Lower electrical conductivity compared to carbon.
• Relatively unreactive in its crystalline form.
• Used in electronics industry to manufacture semiconductors and computer chips.
• Important in metallurgy as a component of alloys.

Properties and Uses of Germanium

• Silvery-white, brittle, hard metal.
• More reactive than silicon.
• Used in making semiconductors and transistors.
• Used in resistance thermometers.

Properties and Uses of Tin

• Exists in three allotropic forms (grey, white, rhombic)
• Relatively unreactive.
• Malleable in its stable white form.
• Used for coating metals (e.g., tin plating of steel).

Properties and Uses of Lead

• Bluish-grey metal; high malleability but low ductility.
• Relatively unreactive.
• Used extensively in lead-acid batteries.
• Used in pipes, containers, and other applications.
• Toxic nature.

Chemistry of Group 14 Elements: Compounds

• Oxides and Oxoacids: Carbon forms numerous oxides and oxoacids (CO, CO2, H2CO3). Other group elements have more basic oxides down the group.
• Halides: Tetrahalides are known for C, Si, Ge, Sn, and Pb; lead halides are less stable, and often ionic.
• Hydrides: Group 14 elements form hydrides such as CH4, SiH4, GeH4, etc.; The stability decreases as you move down the group

Carbides, silicides, germides, stannides and plumbides

• Different types of carbides form depending on the nature of the reacting metal and carbon.
• A variety of silicides, germides, stannides, and plumbides are also known, and their properties vary depending upon their particular type.

Silicates

• Silicates are the most common group of compounds present in the Earth's Crust;
• Structure of silicates vary.
• Many different types of silicate compounds exist which can have different structures depending on their composition.