Carbon Group

What oxidation states are common in Group 14?

• Carbon & silicon: only +4

• Germanium, tin, lead: +2 and +4

• Lead prefers +2 due to the inert pair effect

How does bonding character change down Group 14?

• Carbon: nonmetal, covalent

• Silicon, germanium: metalloids, covalent

• Tin, lead: borderline metals, more metallic but still with covalent character

Why are π bonds common in carbon but not in silicon?

Carbon’s shorter bond lengths and small p orbitals allow strong p–p overlap; silicon’s larger orbitals weaken π bonding.

What type of π bonding becomes stronger down the group?

p–d π bonding, due to increased orbital size and favorable lobe orientation.

Why can silicon be pentavalent, but carbon cannot?

Silicon’s larger size and available d orbitals allow expanded valence shells; carbon lacks d orbitals.

What structure do carbon, silicon, and germanium adopt in the solid state?

Diamond-like tetrahedral structures.

What are the two allotropes of tin, and what happens at cold temperatures?

• White tin: metallic, shiny, malleable

• Gray tin: brittle, diamond-like

• Cold triggers transformation to gray tin → structural breakdown (tin pest)

  

What are interstitial carbides, and how are they formed?

Carbon atoms fit into octahedral holes in metal lattices (e.g., steel), forming hard, high-melting alloys.

Which carbon bonds are especially strong and important in coordination chemistry?

• C–O bonds → CO ligand

• C–N bonds → CN ligand

What are silanes, silicones, and silicates?

• Silanes: Compounds like tetramethylsilane (TMS)

• Silicones: Si–O–Si backbone with R-groups

• Silicates: Salts with Si–O anions

How is pure silicon prepared?

By high-temperature reduction of SiO₂:

• SiO₂ + C → Si + CO

• SiO₂ + Mg → Si + MgO

What are key applications of carbon?

Drugs, fuels, biomolecules, essentially limitless

What are key uses of silicon?

• Microchips and semiconductors

• Al/Si alloys for automotive parts

What are some uses of germanium?

• Transistors, diodes

• Replaces TiO₂ in glass for fiber optics

• Night vision equipment

What are the uses of tin (Sn)?

• Non-toxic, doesn't rust

• Plating to prevent corrosion

What is lead (Pb) used for?

• Lead-acid batteries

• Among the first rechargeable batteries, delivers high currents