Carbon
Atomic number
of hydrogen is 1. Hence hydrogen has one electron in its K shell and it
requires one more electron to fill the K shell. So two hydrogen atoms share
their electrons to form a molecule of hydrogen, H2.shared pair of electrons is
said to constitute a single bond between the two hydrogen atoms atom of oxygen
has six electrons in its L shell (the atomic number of oxygen is eight) and it
requires two more electrons to complete its octet each nitrogen atom in a
molecule of nitrogen contributes three electrons giving rise to three shared pairs
of electrons. This is said to constitute a triple bond between the two atoms Methane
is widely used as a fuel, is a major component of bio-gas and Compressed
Natural Gas (CNG)/LNG(LIQUID NATURAL GAS)Carbon is tetravalent because it has
four valence electrons. In order to achieve noble gas configuration, bonds formed
by the sharing of an electron pair between two atoms are known as covalent
bonds. Since the electrons are shared between atoms and no charged particles
are formed, such covalent compounds are generally poor conductors of
electricity. Allotropes of Carbon:
Carbon is found in various forms, for eg. Graphite, diamond, etc. These are called allotropes. difference lies in the manner in which the carbon atoms are bonded to one another. In graphite 2 Carbon atoms are connected to 1 carbon with single bond & 1 carbon with double bond. Diamond is the hardest substance. graphite is smooth and slippery. Fullerenes form another class of carbon allotropes. Fullerenes form another class of carbon allotropes named after its scientist looks like football.
1. What would
be the electron dot structure of carbon dioxide which has the
formula CO2?
Answer:
2. What would
be the electron dot structure of a molecule of Sulphur which is
made up of
eight atoms of Sulphur? (Hint – The eight atoms of Sulphur are joined
together in the
form of a ring).
Answer:
(i) It could gain four electrons forming C4– anion. But it would be difficult
for the nucleus with six protons to hold on to ten electrons, that is,
four extra electrons.
(ii) It could lose four electrons forming C4+ cation. But it would require
a large amount of energy to remove four electrons leaving behind a
carbon cation with six protons in its nucleus holding on to just two
electrons.
Carbon overcomes this problem by sharing its valence electrons with
other atoms of carbon or with atoms of other elements. Not just carbon,
but many other elements form molecules by sharing electrons in this
manner. The shared electrons ‘belong’ to the outer shells of both the
atoms and lead to both atoms attaining the noble gas configuration.
Methane is widely used as a fuel, is a major
component of bio-gas and Compressed Natural Gas (CNG)
Carbon is tetravalent
Covalently bonded
molecules are seen to have strong bonds within the molecule, but inter
molecular forces are small. This gives rise to the low melting and boiling points. Since the electrons are shared between atoms and no charged particles are formed, such covalent compounds are generally poor conductors of electricity
Hetero
Functional Formula of
atom
group functional group
Cl/Br Halo-
(Chloro/bromo) —Cl, —Br
(substitutes
for
hydrogen atom)
Oxygen 1.
Alcohol —OH
Activity 4.2
1.
Calculate the
difference in the formulae and molecular masses for (a) CH3OH and C2H5OH (b) C2H5OH
and C3H7OH, and (c) C3H7OH and C4H9OH.
2.
Is there any
similarity in these three? YES OH is common
3.
Arrange these
alcohols in the order of increasing carbon atoms to get a family. Can we call
this family a homologous series?
4.
Generate the
homologous series for compounds containing up to four carbons for the other
functional groups given in Table 4.3.
1.
|
|
Molecular
mass |
Difference of
molecular mass |
Difference in
molecular formula |
|
|
(a) |
CH3OH
and C2H5OH |
32 amu and 46
amu |
14U |
CH2 |
|
(b) |
C2H5OH
and C3H7OH |
46 amu and |
14U |
CH2 |
|
(c) |
C3H7OH
and C4H7OH |
60 amu and |
14U |
CH2 |
2.
Yes OH
functional group is common
3.
CH3OH, C2H5OH, C3H7OH, C4H9OH.
Yes, It is a homologous series of alkane alcohols as each
successive member of the series differs by - CH2 unit from
proceeding member
|
Hetero atom |
Functional
group |
Formula of
functional group |
|||||||||||||||||||||||||||||||||||||||||
|
CL/Br |
Halo -
(Chloro/Bromo) |
- Cl, - Br |
|||||||||||||||||||||||||||||||||||||||||
|
Oxygen |
1.
Alcohol 2.
Aldehyde 3.
Ketone 4.
Carboxylic acid |
5.
-OH 6.
9.
11.
|
§
Answer:
Chloro (-CI)
--> CH3CI, C2H5CI,C3H7CI,C4H9CI.
Aldehydes --> CH3CHO,C2H5CHO,C3H7CHO,C4H9CHO.
Ketone -->CH2CO,C2H4CO,C3H6CO,C4H8CO.
Carboxylic acids--> CH2COOH, C2H4COOH, C3H6COOH,
C4H9COOH.
(i) Homologus series having Choloro (-Cl)
functional group: CH3Cl, C2H5Cl, C3H7Cl,
C4H9Cl.
(ii) Homologus series having Aldehydes
functional group: CH3CHO, C2H5CHO, C3H7CHO,
C4H9CHO.
(iii)Homologus series having Ketone functional
group: CH2CO, C2H4CO, C3H6CO,
C4H8CO.
(iv) Homologus series having Carboxylic acids
functional group:CH2COOH, C2H4COOH, C3H6COOH,
C4H9COOH.
Q U E S T I O N
S
1. How many
structural isomers can you draw for pentane?
Answer: Structural
isomer of pentane are
n-pentane
2-methylbutane
2,
2-dimethylpropane
2. What are the two properties of carbon which
lead to the huge number of
carbon compounds
we see around us?
Answer: Two
properties of carbon which lead to the huge number of carbon compounds we see
around us are
• Carbon has 4
valence electrons which are actually a high number of valency.
• Covalent bonding
happens easily with carbon atoms and numerous others such as
oxygen,
chlorine, nitrogen, Sulphur, hydrogen and etc.
3. What will be
the formula and electron dot structure of cyclopentane?
Answer:
4. Draw the
structures for the following compounds.
(i) Ethanoic
acid
(ii)
Bromopentane*
(iii) Butanone
(iv) Hexanal
Answer: i)
ii)
4 Carbon and its compounds
iii)
iv)
5. How would
you name the following compounds?
(i) CH3—CH2—Br
(ii)
(iii)
Answer:
(i) Bromoethane
(ii) Methanal
or Formaldehyde
(iii) Hexyne
Naphthalene ball burning
Camphor burningAlcohol Burning
Activity
Activity 4.5
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