1 Group 14: The Carbon Group
Group 14: The Carbon Group
Carbon is all around us. Perhaps you have heard of Carbon Dioxide (CO2) or Methane (CH4),
the most common molecules containing carbon. All kinds of scientists study carbon-biologists investigating the origins of life, oceanographers measuring the acidification of the
oceans, and engineers developing diamond films for their tools, to name just a few. This
article will focus on the periodic properties of the carbon group and include brief discussions
of the individual properties of carbon, silicon, tin, lead, germanium, and ununquadium.
Contents
1. Introduction
2. Individual Properties
2.1. Carbon
2.2. Silicon
2.3. Tin
2.4. Lead
2.5. Germanium
2.6. Ununquadium
3. Outside links
4. References
5. Problems
6. Contributors
Introduction
The carbon group, Group 14 in the p block, contains carbon (C), silicon (Si), germanium
(Ge), tin (Sn), lead (Pb), and ununquadium (Uuq). These elements have only two electrons
in the outermost p orbital. That is, their valence electron configuration is ns2np2. They tend
to have oxidation states of +4 and, for the heavier elements, +2 due to the inert pair effect.
Figure 1: Row 14 in the Periodic Table
2 Group 14: The Carbon Group
Members of this group conform well to general periodic trends. The atomic radii increase as
you move down the group, and ionization energies decrease. Metallic properties increase as
you move down the group. Carbon is a non-metal; silicon and germanium are metalloids;
and tin and lead are poor metals (meaning, they do not conduct heat and electricity as well as,
say, copper.)
Individual Properties
Atomic Atomic
Classification
#
Mass
Electron
Configuration
Element
Symbol
Carbon
C
6
12.011
Non-metal
[He]2s22p2
Silicon
Si
14
28.0855
Metalloid
[Ne]3s23p2
Germanium
Ge
32
72.61
Metalloid
[Ar]3d104s24p2
Tin
Sn
50
118.710
Metal
[Kr]4d105s25p2
Lead
Pb
82
207.2
Metal
[Xe]4f145d106s26p2
Ununquadium
Uuq
114
287
Metal
[Rn]5f146d107s27p2
Carbon
Carbon is the fourth most abundant element on earth. Carbon is a very special element. It's
what makes organic molecules organic. It is the "backbone" of biology. Why is this? Why
don't we have life based on silicon, or some other element, like iron? Carbon has two
important qualities: small size and a unique electron configuration. Since its small, the porbital electrons overlap considerably and enable pi bonds to form. Compare the molecular
structures of CO2 and SiO2 below.
CO2 has double bonds between carbon and oxygen, whereas SiO 2 has single bonds. Note: The
CO2 molecule can exist on its own, in the gas phase. The SiO2 molecule, on the other hand, is
always within a network of covalent bonds.
3 Group 14: The Carbon Group
The electron configuration of Carbon allows it to form very stable bonds with oxygen and
hydrogen. These bonds can store an enormous amount of energy. Formation and
combustion of these bonds (the carbon cycle) drives life on earth.

Carbon fixation: In photosynthesis, plants use energy from the sun and chlorophyll
molecules to turn gaseous carbon dioxide from the atmosphere into simple carbohydrates,
like glucose.
6CO2 + 6H2O + energy → C6H12O6 + 6O2

Carbon combustion: In respiration, plants and animals combust carbohydrates and use the
energy released to fuel their activities -- growth, movement, etc. In addition, the
combustion of carbohydrates found in fossil fuels powers much of modern life.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Carbon is very popular for having many allotropes. It is second next to sulfur as the element
with the most allotropes. Carbon has several solid state allotropes: graphite, diamond and
fullerenes (or a more memorable name-Buckyball). In graphite, sheets of carbon rings can
easily slide past each other, making this allotrope ubiquitous in pencils. Graphite is also used
in lubricant because it is arranged in planes that can easily slide pass one another. Graphite is
also the most thermodynamically stable allotrope of carbon. Carbon has high melting and
boiling points. In diamonds, each carbon atom is bonded to four others in a tetrahedral
arrangement, resulting in the hardest naturally-occurring substance known. This hardness,
combined with a good ability to dissipate heat, makes diamonds and diamond films an
excellent material in drill bits and other machine parts. Fullerenes (named after R.
Buckminster Fuller) and nanotubes are a series of carbon allotropes in which carbon rings
form more complex forms -- soccerball-like molecules (C60) or tubes that resemble a cylinder
made of chicken wire.
Graphite and diamond.
4 Group 14: The Carbon Group
Silicon
Although silicon plays a much smaller role in biology, it still plays an important role in our
world. It is the second most common element in the earth's crust (after oxygen) and is the
backbone of the mineral world. It is neither a metal or nonmetal, but a metalloid. Silicon is
an inert metal, mainly reacting with halogens. It may have acted as a catalyst in the formation
of the earliest organic molecules (Sadava 62). Plants depend on silicates (such as [SiO4]4-) to
hold nutrients in the soil, where their roots can absorb them (Sadava 787). People around the
world have been using silicon (primarily in the silica SiO2 molecule) for millenia in the
creation of ceramics and glass. In more recent history, the name "Silicon Valley" attests to
its importance in the computing industry-- if carbon is the backbone of human intelligence,
silicon is the backbone of artificial intelligence. Silicon is found in beach sand and is useful
in making concrete and brick.
Tin
Tin is a soft, malleable metals with a low melting point. It has two solid-state allotropes at
regular temperatures and pressures. At higher temperatures (above 13°C), tin exists as white
tin and is often used in alloys. At lower temperatures, tin can transform into grey tin; it loses
its metallic properties and turns powdery. This could cause the disintegration of items made
from white tin alloys that have been exposed to the cold for long periods of time. The pipes
in Europe's great pipe organs are a classic victim of this "tin pest." When a crystalline is
broken, a "tin cry" is heard; this happens when a bar is bent. Most of us probably encounter
tin (grey tin) every day in our kitchens, where we find it preserving our canned goods; the
cans are iron but are plated with tin to prevent them from rusting. Tin is malleable, ductile,
and a crystalline. It has 27 isotopes-9 that are stable and 18 that are not stable. It is a
superconductor at low temperatures. Tin reacts with alkalis, acid salts, and strong acids.
5 Group 14: The Carbon Group
Lead
Lead, aka plumbate, is similar to lead in that it is also a soft, malleable metal with a low
melting point. It is used to be common in water and sewage pipes-hence the terms plumber
and plumbing. Lead is toxic to humans, especially children. Even low levels of exposure
can cause nervous system damage and can prevent proper production of hemoglobin (the
molecule in red blood cells responsible for bringing oxygen to your body). Because of this,
there has been a concerted effort to reduce people's exposure to lead - we now buy unleaded
gasoline and unleaded paint (Petrucci 906-908). Wikipedia has a neat article on the history
and physiology of lead poisoning. Lead usually has an oxidation state of +2 or +4, especially
when it is stable.
Germanium
Germanium is a rare element that is used in the manufacture of semi-conductor devices. The
physical and chemical properties of germanium are very similar to that of Silicon. The semimetal is found in coal, ore, and germanite. The color is gray-white crystalline.
Ununquadium
Ununquadium (Uuq) is also known as Element 114. It was found in 1999 by scientists in
Dubna. It is radioactive.
6 Group 14: The Carbon Group
Outside links
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History Channel segment (via YouTube) on carbon - explains its basic structure, and
what makes diamonds so special
Wikipedia article on nanotubes - amazing structural properties and potential applications
Wikipedia article about tin and its allotropes
Wikipedia article on lead poisoning
Arnáiz, Francisco J.; Pedrosa, María R. "Microscale Transformations of Some Lead
Compounds. A Cycle for Lead Minimizing the Production of Wastes." J. Chem.
Educ. 1999 76 1687.
Schneider, Maxyne, S. S. J. "Lead poisoning danger in pencils (L)." J. Chem.
Educ. 1972, 49, 379.
Web Elements
Chemical Elements
References
1. Petrucci et al. General Chemistry: Principles & Modern Applications, 9th Edition. New
Jersey: Pearson Education, Inc., 2007.
2. Sadava et al. Life: The Science of Biology, 8th Edition. Sunderland, MA: Sinauer
Associates, Inc., 2008.
Problems
1. Recall the metallic properties. What makes tin and lead "poor" metals?
2. What makes graphite such a good material for pencil lead?
3. What makes diamonds so hard?
4. Why is tin used to plate iron cans?
5. Why are +2 and +4 the most common oxidation states of metals in this group?
Answers
1. They do not conduct heat or electricity very well.
2. It is composed of flat sheets, which are weakly bonded to one another, so they
easily slide past each other and rub off on your paper.
3. Each carbon atom forms bonds with four other carbon atoms in a tetrahedral
crystal. This arrangement is extremely strong.
4. The tin plating prevents the iron can from oxidizing (rusting).
5. Since the valence electron configuration is ns2np2, the atoms tend to lose
either all four outer shell electrons (resulting in a charge of +4) or, because of
7 Group 14: The Carbon Group
the inert pair effect, it may lose just the s electrons (resulting in a charge of
+2).
Contributors
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Elizabeth Sproat
Jessica Lin
Vancy Wong