Silicon vs. Carbon
Different atoms?
Hypothesis
Carbon
Silicon
We believe that silicon and carbon are made up of different
atoms.
The following information should help to prove our hypothesis.
FACTUAL EVIDENCE
General Properties
Carbon
Name: Carbon
Symbol: C
Atomic Number: 6
Elemental Category: Non-Metal
Atomic Mass: appx.12 amu
Electron Configuration: 1s2 2s2 2p2
Allotropes: There are 12 known
allotropes of carbon (diamond,
graphite, etc.)
Carbon is the basic component of life
and is found in almost everything (fats,
proteins, sugar, DNA, etc)
Silicon
Name: Silicon
Symbol: Si
Atomic Number: 14
Elemental Category: Metalloid
Atomic Mass: appx. 28 amu
Electron Configuration: 1s2 2s2 2p6 3s2 3p2
Allotropes: There are 2 main
allotropes (crystalline silicon and
amorphous silicon). There is also a
possibility of two more allotropes
(Polycrystalline and microcrystalline
silicon)
*An allotrope is a variant of a substance consisting of only one type of atom (element). It is a new molecular
configuration, with new physical properties.*
Atomic Properties
Carbon
Proton Number: 6
Neutron Number: 6
Electron Number: 6
Oxidation States: 2, +4
Crystal Structure: hexagonal (graphite)
tetrahedral (diamond)
unpredictable (coal)
Electronegativity: 2.55 (pauling scale)
Atomic Radius: 70 pm (picometres)
Isotopes: Has 15 known isotopes – the
three naturally occurring are:
12C, 13C and 14C.
Orbits: Highest orbital level is p. Has
no d orbit.
Silicon
Proton Number: 14
Neutron Number: 28
Electron Number: 14
Oxidation States: 4
Crystal Structure: diamond
Electronegativity: 1.90 (pauling scale)
Atomic Radius: 111 pm (picometres)
Isotopes: Has numerous isotopes
ranging from 22Si to 44Si.
Orbits: Highest orbit level is d.
*Electronegativity describes the ability of an atom to attract electrons towards itself in a covalent bond. An atom's
electronegativity is affected by both its atomic weight and the distance that its valence electrons are from the nucleus. The
higher the electronegativity number, the more an element or compound attracts electrons towards it.*
*The atomic radius of an element is a measure of the size of its atoms, usually the distance from the nucleus to the
boundary of the surrounding cloud of electrons.*
Chemical Properties
Carbon
Silicon
Bonds: Forms strong, stable bonds with itself
and other elements.
Reacts with air: yes, oxidizes to form carbon
dioxide (CO2) [with heat]
Reacts with Hydrogen: yes, reduces to
methane.
Can create Hydrocarbons: yes
Bonds: Forms weaker bonds.
Carbon is a connecting block in “Organic
Chemistry,” the chemistry of life (also the
chemistry required to produce fuels, solvents,
plastics, dies, pharmaceuticals,etc.).
Silicon reacts vigorously with halogens to
form silicon tetrahalides especially fluorine
since it takes place at room temperature but
the others requiring warming over 300°C.
Carbon can create four covalent bonds
allowing it to link to itself in order to create
carbon chains of different lengths/
configurations, or to connect to non-carbon
atoms in order to form compounds with unique
and specialized chemical properties.
Reacts with air: yes, reacts to form silcon
dioxide (SiO2) [with heat]
Reacts with Hydrogen: No
Can create Hydrocarbons: No
Silicon does not react with most acids under
normal conditions but is dissolved by
hydrofluoric acid, HF.
Silicon is attacked by bases such as
aqueous sodium hydroxide to give silicates,
which are highly complex chemicals
containing the anion [SiO4]4-
Physical Properties
Carbon
Electrical Conductivity: 0.07 * 106 S cm -1
Electrical Resistance: 3.5 * 10-5 Ω
Density: Ranging from 2.267 g/cm3
(graphite) to 3.515 g/cm3
(diamond)
Phases: Has no liquid phase, only a
solid and a gas phase.
Sublimation Point: 3642 ºC
Flammability Class: Combustible solid
(graphite)
Thermal Conductivity: 1.29 W/cmK
Silicon
Electrical Conductivity: 1.2 * 10-5S cm-1
Electrical Resistance: 6.40 * 102 Ω
Density: 2.57 g/cm3
Phases: Has a liquid phase along with
a gas and solid phase as well.
Boiling Point: 2355 ºC
Flammability Class: Combustible
solid in powdered form.
Thermal Conductivity: 1.48 W/cmk
*Ω is an ohm, a unit used in the international system of measurements to measure resistance. *
*W stands for watts which is a unit of power that measures rate of energy conversion.*
*K stands for Kelvin which is a unit of temperature and is one of the seven SI base units.*
PHYSICAL EVIDENCE
*Please be patient for slow videos*
Physical Properties
Colour
Carbon
(1st substance shown in video)
- Usually black in colour however clear
and colourless when in diamond form.
- Lacks luster
Silicon
(2nd substance shown in video)
- Silver and black in colour.
- Lustrous
Mechanical Properties
Hardness
Carbon
A fingernail, with a hardness of 2.5 mohs,
was able to scratch the carbon, however not
very well. Therefore this allotrope of carbon
most likely has a hardness of less than 2.5
mohs.
Carbon has varied hardness levels. It
can vary from 0.5 mohs (graphite) to
10.0 mohs (diamond.
Silicon
A knife, with a hardness of 5.5 mohs was
unable to scratch the silicon. Therefore
silicon has a hardness over 5.5 mohs.
Silicon has a hardness of 7 mohs.
Explanation
-
-
-
Chemical and physical properties of matter depend on the electron cloud
surrounding the atoms.
Therefore they also depend on the number of protons in the nucleus.
Basically the chemical and physical properties are based on the atomic
number.
Silicon and carbon also have different electron configurations, which means
the electron clouds are different.
Since carbon and silicon have so many physical, chemical and mechanical
differences, it is easy to say that these two elements are made of different
atoms. Not to mention that they have two different atomic numbers (which
means they have different amounts of subatomic particles – different, or
differently arranged, atoms.)