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
What are the 2 oxides of C
CO
CO2
Properties of CO
Colorless, odorless, highly poisonous
C-O bond length is short (triple bond)
Highly unstable due to + charge on O
Incomplete combustion of C gives CO
Why is CO highly unstable
Highly unstable due to + charge on O
How is CO formed
Incomplete combustion of C
Features of CO
- Good ligand (due to loan pairs on C)
- Good reducing agent (CO easily oxidizes to CO2)
- Used in metal extractions (iron)
Why is CO a good ligand
due to loan pairs on C
Why is CO a good reducing agent
CO easily oxidizes to CO2
Describe CO2
- Colorless, odorless, non-poisonous and slightly water soluble gas
- Under london forces, CO2 is solidified under lower temperatures and is called dry ice
- Dry ice is used as a freezing agent in food industry, and produces artificial rain
What’s dry ice
Under london forces, CO2 is solidified under lower temperatures and is called dry ice
Write the importance of dry ice
- freezing agent in food industry
- produces artificial rain
Identification of CO2
CO2 gas is passed through a lime water sample and a milky white precipitate of CaCO3 is given
With excess CO2 precipitate dissolves to give a colorless solution
Ca(OH)2 + CO2 — CaCO3 + H20
CaCO3 + CO2 —> Ca(HCO3)2
Write the reactions of CO2 identification
Ca(OH)2 + CO2 — CaCO3 + H20
CaCO3 + CO2 —> Ca(HCO3)2
Name the oxoacid of C
H2CO3
How is H2CO3 prepared?
Dissolving CO2 in water
CO2 (g) –> CO2 (aq)
CO2 (aq) + H20 –> H2CO3 (aq)
Steps of ionization of H2CO3
H2CO3 + H20 –> HCO3- + H3O+
HCO3- + H20 –> CO3 2- + H3O+
Why does H2CO3 ionize?
Because it’s a diprotic weak acid
