Group 14 Flashcards
(27 cards)
Name the group 14 elements
Carbon, silicon, germanium, tin, lead
Which of the group 14 elements are non metals, metalloids and metals?
carbon - non metal silicon - metalloid germanium - metalloid tin - metal lead - metal
Describe the diamond structure
- sp3 hybridisation
- 4 x sigma bonds
- extended covalent structure
- Si, Ge and Sn can also form a diamond structure
Describe the graphite structure
- sp2 hybridisation
- sigma and pi bonding in plane
- weak interplanar attractions
- no silicon analogue bc the Si-Si p-pi p-pi bonds are too weak
What is the buckyball?
An allotrope of carbon, C60, also known as buckminster fullerene, soluble in hydrocarbons, truncated icosahedron
How is fullerene synthesised?
Electric discharge between two graphite electrodes in an inert atmosphere, this produces soot and fullerenes
Describe the structure of graphene
single layer of graphite, 2010 Nobel prize, prepared by ‘exfoliation’ of graphite with scotch tape.
List 2 uses of carbon
Graphite - lubricant
Diamond - industrial cutting tools
coal - reductant for metal extraction
what are silicon, germanium, tin and lead used for?
silicon - semiconductor - electronics
germanium - semiconductor - electronics
tin - float glass process, alloyed w/ Cu - bronze
lead - radiation shields
Why is SiX4 readily hydrolysed?
because of the polarity of its bonds
Draw the reaction of 2 eqs of pyridine with GeCl4 and explain why the reaction happens
forms 6 coordinate adduct with the GeCl4, this is because GeCl4 is lewis acidic. The other MX4 molecules are lewis acidic too. (Ge, Sn, Pb)
How does the stability of the oxidation state +2 change from Ge to Pb
The stability of the +2 oxidation state increases down the group. We can see this in the reaction PbCl4 –> PbCl2 + Cl2 at room temperature. Pb(IV) halides are unstable
Which bonds are weaker C-C and C-H or Si-Si and Si-H?
The silicon bonds are weaker because silicon is a larger atom, so the orbital overlap is smaller
Why are silanes highly reactive?
Because of their lewis acidity
What is the general formula for silanes?
Si n H 2n+2
Which of the following should be kept in anhydrous conditions and why? CX4, SiX4
SiX4 is susceptible to hydrolysis because it is lewis acidic/ Si can be hypervalent, should be kept in anhydrous conditions or it will form Si(OH)4. CX4 isn’t susceptible to hydrolysis, not lewis acidic
Draw the bonding in carbon monoxide
triple bond one lone pair on each
Describe the appearance, pH and reactivity of CO
It is a colourless, odourless gas. It is a Lewis acid because of the lone pair on each atom. It reacts well as a ligand for transition metals because of the C lone pair, therefore can also be used as a feedstock for chemical industry (can form complexes w/ TMs). It binds to haemoglobin 100x more strongly than oxygen.
Describe the appearance, pH and reactivity of CO2
CO2 is a colourless odourless gas. No liquid phase at atmospheric pressure (67 atm it’s liquid). Solid is called cardice. Weak acid when dissolved in water. Used as a refrigerant, in fizzy drinks etc.
How does the strength of the Si-O bond compare to the C-O bond?
Si-O stronger because of polarity
How does the Si=O strength compare to the C=O strength?
The Si=O bond isn’t known because it doesn’t occur due the difference in p orbital size between Si and O. The C=O bond however is strong. Si form 4 single bonds to O while C form 2 double bonds.
Describe the structure of CO2 compared to SiO2
CO2 is covalent and molecular
SiO2 is covalent and polymeric - it forms beta quartz and cristobalite which has a fcc structure
Draw the orthosilicate anion and give two examples of how it condenses
[SiO4]4-
tries to condense to species with less charge on each atom. Pyrosilicate [Si2O7]6- . Cyclic metasilicate {[SiO3]2-}
Name two uses of sheet silicate [Si2O5]2-
Talc and white asbestos
