chemistry allotropes, occurance, properties,uses

1. THE BEST SCIENTIST IS OPEN TO EXPERIENCE AND BEGINS WITH
ROMANCE - THE IDEA THAT ANYTHING IS POSSIBLE. - Ray Bradbury –
DON’T SAY YOU DON’T HAVE ENOUGH TIME. YOU HAVE EXACTLY THE SAME
NUMBER OF HOURS PER DAY THAT WERE GIVEN TO HELEN KELLER,
PASTEUR, MICHAELANGELO, MOTHER TERESEA, LEONARDO DA VINCI,
THOMAS JEFFERSON AND ALBERT EINSTEIN. - H. Jackson Brown, Jr.-

2. VSEPR THEORY ALLOWS US TO PREDICT
MOLECULAR GEOMETRIES BASED ON THE NUMBER
OF ELECTRON DOMAINS A BONDING ATOM HAS.
TO FURTHER EXPLAIN HOW ATOMS BOND TO
FORM MOLECULES, CHEMISTS USE THE VALENCE
BOND THEORY.
THE VALENCE BOND THEORY SAYS THAT ATOMIC
ORBITALS FROM ADJOINING ATOMS CAN
OVERLAP TO FORM BONDS.
TO EXPLAIN ALL OF THE BOND ANGLES AND
SHAPES THAT RESULT, THIS THEORY SAYS THAT
INDIVIDUAL ATOMIC ORBITALS CAN AVERAGE
OUT OR HYBRIDIZE TO GIVE DIFFERENT SHAPES.

3. http://www.mhhe.com/physsci/chemistry/essentialche
mistry/flash/hybrv18.swf

4. CARBON CHEMISTRY
Atomic Number 6
Atomic Mass Average: 12.011
Melting Point: 3823 K (3550°C or 6422°F)
Boiling Point: 4098 K (3825°C or 6917°F)
Density: 2.267g/cu.cm.
CARBON HAS FIVE KNOWN ALLOTROPES:
AMORPHOUS
GRAPHITE
DIAMOND
FULLERENE
MAGNETIC CARBON NANOFOAM
NOTE: TUNGSTEN HAS THE HIGHEST MELTING POINT OF ANY
METAL AT 3422o C. IRON HAS A MELTING POINT OF 1535o C.

5. protons neutrons mass number
carbon 12 6 6 12
carbon 13 6 7 13
carbon 14 6 8 14
ISOTOPES OF CARBON

6. CARBON DATING
THE AMOUNT OF 14C REMAINS APPROXIMATELY
CONSTANT IN THE ATMOSPHERE BECAUSE 14C IS
BEING FORMED IN THE UPPER ATMOSPHERE THROUGH
NEUTRON CAPTURE.
14
7N + 1n  14
6C + 1p
CARBON-14 DECAYS WITH A HALF LIFE OF 5715
YEARS.
14
6C  14
7N + 0e
WE ASSUME THAT THE RATIO OF CARBON 14 TO
CARBON 12 HAS BEEN CONSTANT FOR AT LEAST
50,000 YEARS.

7. ATOMIC STRUCTURE OF CARBON
THIS MEANS THAT CARBON HAS FOUR
VALENCE ELECTRONS.

8. The electronegativity (EN = 2.55) is too small to
allow carbon to form C4- ions and too large to
allow carbon to form C4+ ions.
Carbon forms covalent bonds.
To reach inert gas configuration, it needs a share
in 4 more electrons. It can do this several ways.
One 2s electron can shift up to the vacant 2p
orbital. These orbitals can hybridise to give 4
sp3 hybrids. This would allow it to form 4
covalent bonds (sigma bonds) with 4 other
elements.

10. HYBRIDIZATION OF 3 P ORBITALS AND 1 S
ORBITAL TO GIVE 4 SP3 HYBRID ORBITALS.

11. A SIGMA BOND IS A BOND FORMED WHEN ONE
PAIR OF ELECTRONS IS SHARED BETWEEN TWO
ATOMS.
IN THE CASE OF FOUR SP3 HYBRID ORBITALS,
FOUR SIGMA BONDS COULD BE FORMED WITH
FOUR OTHER ATOMS.
To be equi-distant from each other, these bonds
would be pointing to the corners of a regular
tetrahedron, and the bond angles would be 109.5o.
An example would be methane.

12. HERE ARE THREE WAYS OF REPRESENTING
THE MOLECULE METHANE.

13. SPACE FILLING MODEL

14. ONE ALLOTROPE OF
CARBON THAT USES
SP3 HYBRID BONDING
IS DIAMOND.
ONE CARBON ATOM
IS BONDED TO FOUR
OTHER CARBON
ATOMS.
THIS PROVIDES A
VERY STRONG
STRUCTURE, MAKING
DIAMOND THE
HARDEST MATERIAL
KNOWN.

15. Another way carbon can form bonds is for one 2s
electron can shift up to the vacant 2p orbital.
One electron in the 2s orbital and 2 electrons in
two of the 2p orbitals can hybridise to form
three sp2 hybrid orbitals.
For these three orbitals to be equidistant, they
would be trigonal planar. All would be in the
same plane, and the bond angles would be 120o.
The remaining electron would be in a 2p orbital
at right angles to the plane that the hybrid
orbitals occupied.

18. THIS IS THE TYPE OF BONDING THAT WOULD
BE USED IN GRAPHITE.

19. THE SAME KIND OF BONDING WOULD BE USED
IN FULLERENES.
A C60
FULLERENE

20. Creative Chemistry Interactive Molecular Models -
Carbon Allotropes

21. THE FINAL WAY CARBON CAN BOND WOULD
BE FOR ONE 2S ELECTRON TO SHIFT UP TO
THE VACANT 2P ORBITAL.
THEN, 1 ELECTRON IN ONE OF THE 2P
ORBITALS COULD HYBRIDISE WITH 1
ELECTRON IN THE 2S ORBITAL TO FORM TWO
SP HYBRID ORBITALS.
FOR THESE ORBITALS TO BE EQUIDISTANT,
THEY WOULD BE PLANAR AND 180O APART.
THE TWO REMAINING 2P ELECTRONS WOULD
BE IN 2P ORBITALS AT RIGHT ANGLES TO THE
SP HYBRID OBRITALS.

23. TWO SP HYBRID ORBITALS WITH TWO 2P
ORBITALS.

24. SP BONDING IS NOT USED IN THE FORMATION
OF ANY CARBON ALLOTROPES.
IT IS USED IN FORMATION OF SOME
COMPOUNDS CONTAINING CARBON.
THE TABLE BELOW COMPARES THE PROPERTIES
OF GRAPHITE AND CARBON - TWO ALLOTROPES
OF CARBON THAT USE DIFFERENT
HYBRIDIZATION.

25. BONDING POSSIBILTIES FOR CARBON
THESE BONDING POSSIBILITIES ALLOW
CARBON TO FORM SEVERAL TYPES OF BONDS
WITH OTHER CARBON ATOMS AND WITH
OTHER ELEMENTS.

26. THERE IS AN ENTIRE BRANCH OF CHEMISTRY
DEVOTED TO THE CHEMISTRY OF CARBON
COMPOUNDS - ORGANIC CHEMISTRY.
THERE ARE SEVERAL BRANCHES OF ORGANIC
CHEMISTRY:
1) BIOCHEMISTRY - THE CHEMISTRY OF
LIVING ORGANISMS
2) POLYMER CHEMISTRY - THE CHEMISTRY OF
VERY LARGE MOLECULES OF REPEATING
STRUCTURE
3) ORGANIC SYNTHESIS - THE SCIENCE OF
BUILDING MOLECULES OF GIVEN
STRUCTURES
4) ORGANIC ANALYSIS - COMPOSITION AND
STRUCTURE DETERMINATION

27. http://www.mhhe.com/physsci/chemistry/animations/c
hang_7e_esp/bom5s2_6.swf
THIS LINK DISCUSSES SIGMA AND PI BONDS.

28. BOND #
ELECTRONS
BOND
ORDER
BOND
STRENGTH
BOND
LENGTH
SINGLE 2 1 WEAKEST LONGEST
DOUBLE 4 2
TRIPLE 6 3 STRONGEST SHORTES
T
“A single bond is weaker and has a smaller
density than a double bond and a triple bond,
it is the most stable because it has a lower
level of reactivity meaning less vulnerability in
losing electrons to atoms that want to steal
electrons.”
- Chemwiki -