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Group 14 Flashcards

1
Q

Name the group 14 elements

A

Carbon - silicon - germanium - tin - lead - flerovium

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2
Q

Discuss abundancy of carbon

A
  1. Carbon is 17th most abundant element on Earth

2. It is also found as CO2 in air (0.03%)

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3
Q

Discuss availability of carbon

A
  1. It is available in the elemental state as Diamond, Graphite and Coal
  2. It is available in combined state as metal carbonates, hydrocarbons and CO2
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4
Q

Discuss isotopes of carbon

A

Carbon(12), Carbon(13) and Carbon(14)

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5
Q

Which is the radioactive isotope of carbon? Mention half life

A

Carbon(14) is radioactive in nature

It has a half life of 5770 years and is used for radiocarbon dating

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6
Q

Discuss occurrence of Silicon

A
  1. Silicon is second most abundant element on Earth’s crust

2. It exists in nature as silicates and silica

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7
Q

Discuss occurrence of other metals

A
  1. Germanium occurs in traces
  2. Tin occurs as Cassiterite
  3. Lead occurs as Galena
  4. Flerovium is synthetically produced radioactive element
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8
Q

Cassiterite

A

SnO2

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9
Q

Galena

A

PbS

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10
Q

Atomic number of Fl

A

114

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11
Q

Mass of Fl

A

289 g/mol

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12
Q

Electronic configuration

A

ns2np2

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13
Q

Discuss covalent radius trend

A

From C to Si, there is a notable increase due to increase in number of shells
From Si to Pb, only a small increase is seen due to presence of completely filled d and f orbitals

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14
Q

Discuss ionization enthalpy trend

A
  1. It is higher than group 13 elements

2. It decreases as we go down the group

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15
Q

What is the exception in IE trend

A

There is a small decrease from Si > Ge > Sn (as expected) but there is an increase from Sn < Pb because of poor shielding effect of the d and f orbitals and increase in atomic size

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16
Q

Discuss electronegativity trend

A
  1. Due to decrease in size, group 14 is more electronegative than group 13
  2. Electronegativity values of Si to Pb are almost the same
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17
Q

Discuss physical properties of group 14 elements

A
  1. They are all solids
  2. C, Si are non-metals
  3. Ge is a metalloid
  4. Sn, Pb are soft metals with low MP
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18
Q

Discuss all oxidation states

A
  1. They show +4 and +2 OS

2. Compounds with +4 are generally more covalent because sum of four IEs is quite high

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19
Q

Discuss variation in oxidation states

A
  1. C, Si are very stable in +4 OS
  2. Ge forms stable compounds in both +4 and +2 (more +4 than +2)
  3. Sn is a good reducing agent in +2, forms compounds using both OS
  4. Pb is a good oxidizing agent in +4 and compounds in +2 are stable
  5. C can also show negative OS
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20
Q

Why is one OS more stable than the other down the group

A

+2 is more stable because as we go down the group, ns electrons get more and more resistant towards participation because of shielding effect

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21
Q

Do group 14 elements act as Lewis acids/bases? Why/why not?

A

They have 8 electrons and are hence electron precise elements and do not accept or donate an electron.
However, hydrolyzed compounds of Si, Ge, Sn and Pb accept electron pairs because of availability of d and f orbitals

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22
Q

What kind of oxides are formed

A

Elements in this group form monoxides MO and dioxides MO2

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23
Q

What is the general rule for acidity of oxides

A

Oxides in higher OS are more acidic than the ones in lower states

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24
Q

Comment on acidity of group 14 oxides

A
  1. CO2, SiO2, GeO2 are all acidic
  2. SnO2 and PbO2 are amphoteric
  3. CO is neutral
  4. GeO is predominantly acidic
  5. SnO and PbO are amphoteric
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25
Q

Discuss reactivity with water

A
  1. C, Si and Ge are unaffected by water
  2. Sn decomposes water to release SnO2 and H2 gas
  3. Pb does not react with water due to protective oxide layer formation
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26
Q

What kind of halides are formed

A

MX2 (ionic) and MX4 (covalent)

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27
Q

Discuss features of MX2

A
  1. They are ionic
  2. Their stability increases down the group
  3. They are sp hybridized and linear in shape
  4. Pb and Sn form MX2
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28
Q

Discuss features of MX4

A
  1. They are covalent
  2. Their stability decreases down the group
  3. They are sp3 hybridized and tetrahedral in shape
  4. C, Si, Ge form these
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29
Q

Why does PbI4 not exist?

A

Because when the first Pb-I bond is formed, not enough energy is released to unpair 6s2 electrons and send them to a higher energy level to have 4 unpaired electrons for 4 iodine atoms

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30
Q

Discuss halide solubility

A
  1. Except CCl4, all halides are hydrolyzed because central atom can accommodate the lone pair of electrons from oxygen atom of water molecule
31
Q

Discuss anomalies in carbon

A
  1. Carbon has a maximum covalence of 4 unlike the other elements (absence of d orbitals)
  2. Unique ability to show p(pi)-p(pi) bonds with itself and other atoms of similar size
  3. Catenation - links with other carbon atoms to form chains and rings because the C-C bond is very strong
32
Q

Why do heavier elements not show p(pi)-p(pi) bonds?

A

Because their atomic orbitals are too large and diffuse to have effective overlapping

33
Q

Diamond

A
  1. Crystalline lattice
  2. Each C is sp3 hybridized and bonded to 3 other carbons in a tetrahedral way
  3. This structure continues in space to create a rigid three dimensional structure
  4. Extended covalent bonds are hard to break and hence diamond is the hardest substance on Earth
34
Q

Diamond is covalent but still has high MP. Why?

A

Because of its extended directional covalent bonding system, the bonds are extremely difficult to break. Hence, MP is quite high

35
Q

C-C bond length in diamond

A

154 pm

36
Q

Graphite

A
  1. Has layered structure
  2. Each layer consists of planar hexagonal rings with C-C bonds.
  3. Each C is sp 2 hybridized with 3 sigma bonds and 1 pi bond
  4. The electrons are delocalized over the whole structure which makes graphite a good conductor
37
Q

Why is graphite soft and slippery?

A

Because the layers of graphite can cleave easily

38
Q

Distance between layers in graphite

A

340 pm

39
Q

C-C bond length

A

141.5 pm

40
Q

Fullerenes

A
  1. Made by heating graphite in an electric arc in presence of inert gases like He or Ar
  2. The sooty material formed by condensation consists of mainly C(60) molecules with a small amount of C(70) and traces of fullerenes going up to 350
41
Q

Discuss structure of buckminsterfullerene

A

Buckminsterfullerene is the fullerene made of C60

  1. Contains 20 6-membered rings and 12 5-membered rings
  2. A 6 ring can be fused with a 6 or a 5 ring but a 5 ring can only be fused with a 6 ring
  3. All carbons are sp2 hybridized with 3 sigma bonds and the remaining electron delocalized
  4. Has 60 vertices
  5. Contains both single and double bonds
  6. Also called Bucky balls for short
42
Q

Why is Buckminsterfullerene aromatic?

A

Because of presence of delocalized electrons

43
Q

C-C and C=C bond length in BMF?

A

143.5 and 138.3 pm

44
Q

Which is thermodynamically most stable allotrope of carbon?

A

Graphite

45
Q

How is carbon black obtained?

A

By burning hydrocarbons in limited air

46
Q

How is charcoal/coke obtained?

A

By heating wood or coal at high temperatures in absence of air

47
Q

How much is 1 carat

A

200 mg

48
Q

How is CO produced

A
  1. Direct oxidation of C in limited supply of oxygen
    2C + O2 = 2CO
  2. Industrially, it is prepared by dehydration of formic acid using conc H2SO4 at 373 K
    HCOOH + heat + H2SO4 = CO + H2O
  3. Commercially it is produced by passing steam over hot coke
    C + H2O = CO + H2
  4. If air is used instead of steam also, CO can be prepared
    2C + O2 + N2 = 2CO + N2
49
Q

Water gas

A

Also called synthesis/syn gas

CO + H2

50
Q

Producer gas

A

CO + N2

51
Q

Physical Properties and structure of CO

A
  1. Colorless, odorless, tasteless gas
  2. Almost water insoluble
  3. CO has one sigma and two pi bonds
  4. There is a lone pair on both carbon and oxygen
52
Q

Chemical Properties of CO

A
  1. Powerful reducing agent and is used to extract some metals out of their metal oxide ores
  2. The lone pair on the C acts as a donor and results in the formation of metal carbonyls
53
Q

Why is CO poisonous

A

Because CO tends to form a complex with hemoglobin which is more stable than the oxygen-hemoglobin complex. So, hemoglobin will not bind to oxygen and carry it around the body anymore, slowly causing death

54
Q

How is CO2 prepared

A 
1. By heating carbon in excess of air
C + O2(excess) = CO2
2. Industrially, by reacting HCl with CaCO3
2HCl + CaCO3 = CaCl2 + H2O + CO2
3. Commercially, by heating limestone
55
Q

Physical properties and structure of CO2

A
  1. Colorless, odorless, tasteless gas
  2. Low solubility in water
  3. sp hybridized linear molecule
  4. Has 2 sigma and 2 pi bonds
  5. Is involved in resonance
  6. 0 dipole moment
56
Q

CO2 + water = ?

A

H2CO3 - carbonic acid which dissociates in two steps to give (CO3)2-

57
Q

Uses of H2CO3

A

The H2CO3/HCO3- buffer system helps maintain the pH of blood at around 7.26 - 7.42

58
Q

Photosynthesis

A

Process by which plants take in CO2 and water to produce for themselves and humans, releasing oxygen in the process
6CO2 + 12H2O + hv + chlorophyll = C6H12O6 + 6O2 + 6H2O

59
Q

Greenhouse effect

A

The effect of temperature rise due to excess CO2 in the atmosphere due to combustion of fossil fuels, decomposition of limestone, etc.

60
Q

Dry ice

A

Formed when liquified CO2 is allowed to expand quickly

Used to store ice creams and frozen food

61
Q

What is CO2 used for

A
  1. It does not support combustion and is hence used in fire extinguishers
  2. Gaseous CO2 is used in soft drinks
  3. It is also used to manufacture urea
62
Q

Silica

A

SiO2

63
Q

Name some crystalline forms of silica

A

Quartz, tridymite, cristoballite

64
Q

Structure of silica

A
  1. Covalent, 3D network solid
  2. Each Si atom is bound to 4 oxygen atoms and each oxygen atom is bound to 2 Si atoms
  3. Lots of mini tetrahedrons
  4. The entire crystal may be considered as a giant molecule with eight member rings are formed with alternate Si and O2 atoms
65
Q

Chemical properties of silica

A
  1. Almost non-reactive because of high Si-O bond enthalpy
  2. It is attacked by HF and NaOH
    HF + SiO2 = SiF4 + H2O
    NaOH + SiO2 = Na2SiO3 + H2O
66
Q

Kieselghur

A

An amorphous form of silica used in filtration plants

67
Q

Silicones

A
  1. Organosilicon polymers

2. -(R2SiO)- is the repeating unit

68
Q

Manufacture of silicones

A

Hydrolysis of alkyl or aryl substituted silicon chlorides RnSiCl(4-n)

69
Q

Physical properties of silicones

A
  1. Water repelling because they are surrounded by non-polar alkyl groups
  2. High thermal stability
  3. High dielectric strength
  4. Resistant to oxidation and chemicals
70
Q

Silicates

A

Minerals with basic structural unit - (SiO4)4-

Examples - feldspar, zeolite, mica, asbestos

71
Q

Structure of silicates

A

Each Si atom is bound to four oxygen atoms in a tetrahedron fashion
In silicates, either the discrete unit is itself present or a number of such units are joined together by 1/2/3/4 oxygen atoms per silicate units
They can eventually form chains, rings, 3D structures

72
Q

Man made silicates

A

Glass, cement

73
Q

Zeolites

A

When aluminum replaces some of the Si atoms in the 3D network, an overall -ve charge is acquired which is balanced by Na+ or K+ thereby producing feldspars and zeolites

74
Q

Uses of zeolite

A
  1. Catalyst in petrochemical industries for cracking of hydrocarbons and isomerization
  2. ZSM-5 (a zeolite) converts alcohol directly to gasoline
  3. Hydrated zeolites are used as ion exchangers to soften “hard” water

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