14th Group Flashcards
common configuration of 14th group
ns2 np2
Valences of 14th group
2 and 4
How does the metallic character of 14th group elements vary down the group?
It increases
Describe metallic character of C
Non-metal
Describe metallic character of Si and Ge
Metalloids
Describe metallic character of Sn and Pb
Metals
Why do C, Si and Ge have high melting points?
due to formation of network covalent structures
How is carbon found in nature?
- Coal
- Crude Oil
- Calcite (CaCO3)
- Magnesite (MgCO3)
- Dolomite (CaCO3. MgCO3)
What are the allotropic forms of carbon?
graphite, diamond, fullerenes
Describe diamond lattice
- Homo-atomic lattice
- Each C atom tetrahedrally surrounded by 4 other carbon atoms
- All C atoms have sp3 hybridizations
- Due to covalent lattice and strong C-C bonds, special properties can be seen:
- Unreactive
- High MP (than graphite)
- High hardness
- High refractive index
- High density
What are the special properties of diamond due to its covalent lattice?
- Unreactive
- High MP (than graphite)
- High hardness
- High refractive index
- High density
Describe graphite
- 2D network structure. Very strong, hard to break. Therefore, high MP
- These 2D sheets are composed of C atoms
- Each C atom is bonded to 3 other C atoms as a trigonal planar structure - sp2 hybridized
- C-C bond length is less than diamond (141 pm)
- With sp2 hybridization, each C atom has an unhybridized p-orbital with delocalized electrons between 2D layers. So, graphite is a good conductor
- 2D layers are held together by london force, so layers can overlap and form a lubricating property.
- Special properties:
1. good lubricant
2. soft
3. Very high MP
4. high density
What are the special properties of graphite?
- Special properties:
1. good lubricant
2. soft
3. Very high MP
4. high density
Why is graphite a good lubricant?
2D layers are held together by london force, so layers can overlap and form a lubricating property.
Why is graphite a good conductor
With sp2 hybridization, each C atom has an unhybridized p-orbital with delocalized electrons between 2D layers. So, graphite is a good conductor