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Carbon Family

The long form of the periodic table or modern form of the periodic table is an arrangement of all known elements in the increasing order of their atomic number. The entire table contains 18 vertical groups and 7 horizontal rows. There are two series of 14 elements at the bottom of the main table. Entire table can be classified in 4 blocks on the basis of their valence shell electronic configuration of elements.

The s-block elements have their valence electron in s-orbital. First and 2nd groups of the periodic table are part of this block. From 3rd to 12th group, elements are part of d-block elements as their valence electrons enter in d-orbital. They are commonly known as transition elements also due to variable oxidation states. The f-block elements are placed at the bottom of the main table. The first series of f-block is known as lanthanide and 2nd series is called as actinides.

The right side of the periodic table from a 13th group of 18th group are part of the p-block elements. Their valence electrons enter in the p-orbital of the element. The groups of p-block is usually studied group wise from top to bottom. For example 13th group of element is started from boron and is known as Boron family. Similarly 14th group is started from carbon and is known as carbon family. Let’s discuss about 13th group or carbon family.

 

Electronic Configuration of Carbon

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Here are the list of elements, with their electronic configurations.

Element Symbol Atomic No. Electronic Configuration Abundance in Earth's crust (in ppm)
Carbon c 6 [He] 2s2 2p2 320
Silicon Si 14 [Ne] 3s2 3p2 277, 200
Germanium Ge 32 [Ar] 3d10 4s2 4p2 7
Tin Sn 50 [Kr] 4d10 5s2 5p2 40
Lead Pb 82 [Xe] 5d10 6s2 6p2 16

The configurations of carbon family elements shows that they have four electrons in their valence shell. Two electrons are in the 's' sub-shell and the other two, in the 'p' sub-shell. Only Carbon has, in its penultimate shell S2 configuration. All the other elements have either s2, 2p6 (Si) or s2, p6 , d10 (Ge, Sn, Pb) configurations. This is the reason why Carbon differs slightly from the other members of its group.

Carbon Family Characteristics

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Occurrence


Carbon is the only element of the IV A group, which occur in nature in the free state. Carbon is present as diamond, graphite and coal. Carbon also occurs in the combined state, in many organic compounds such as hydrocarbons, carbohydrates, etc. Carbon is also present in the atmosphere as Carbon dioxide.

The next element, Silicon, is the second abundant element after oxygen. It is present in sand, rocks, etc, in the form of silicates or silica. Germanium is a rare element. The last two elements are present in the form of its ores. Tin is present as its oxide ore, as Tin Stone, SnO2. Lead is present as its sulphide ore, Galena, PbS.

Allotropy


Allotropy is a phenomenon by which an element can exist in more than one form. Except Lead, Pb, all the other elements of IV A group of this group show allotropy. These elements exist in different allotropic forms. The different allotropic forms of IV group elements are:

1. Carbon
  • Crystalline forms - Diamond and Graphite
  • Amorphous form - Coal, Coke, charcoal, etc

Carbon Atoms in a Diamond
2. Silicon
  • Crystalline and amorphous form.
  • Amorphous form of silicon is the common form.
3. Germanium

Two crystalline forms, called α and β Germanium.

4. Tin
  • White tin
  • Grey tin
  • Rhombic tin

Atomic volume, atomic size and ionic size


The atomic size and the atomic volume increases as we move down the group, from carbon to lead. The ionic radii for tetravalent cation increases steadily from carbon to lead. The increase in size of the ion is due to the fact that, as we move down the group, an additional shell is being added to each element. Example: Carbon has 2 shells, while the valence electron of Si enters the 3rd shell.

Density


The density in Carbon family increases as we go down the group.

Element
Carbon Silicon
Germanium
Stannous Lead
Density (g/cc) 3.5 for diamond
2.0 for graphite
2.34 5.32 7.26 11.3

Carbon Family Facts

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The change from non-metallic to metallic character with the increase in atomic number is best illustrated by the elements of this group. Carbon and Silicon, the first two elements, are completely non - metallic. But, some electrical properties exhibited by Si shows a little bit of metallic character, thus making it a semi-metal or a metalloid. Germanium exhibits both metallic as well as non-metallic characteristics, thus making it a semi-metal or a metalloid.

The last two elements, tin and lead are distinctly metals.

Carbon Family Facts

The reduction in the effective nuclear charge, with the increase in number of electrons (or the atomic number) and the increase in number of available orbitals with the increase in size of the atom, is the reason for increase in the metallic character, as we move down the group.

Periodic Table Carbon Family

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Carbon family is positioned almost in the middle of the periodic table, separating the metals from the non metals. The non-metallic characteristics starts from this family. Thus, carbon family has the metals on their left, and the non- metals on their right. These elements are placed in the p - block of the periodic table.

Carbon Family Name

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  1. Carbon, silicon, germanium, tin and lead constitute group 14 elements of the long form of periodic table.
  2. These are also known as carbon family after the name of the first element of this group.
  3. They have four electrons in their outermost or valence or the ultimate shell. They constitute a part of representative elements.

Characteristics of the Carbon Family

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1. Melting and boiling points

In comparison with the group 13 elements, the carbon group elements have much higher melting and boiling points. It is also absorbed that the melting and boiling points show a downward trend as we move down the group, though a little haphazardly.

The decrease is sue to the fact that the inter atomic forces of these molecules decrease as we move down. Carbon and silicon form extraordinarily giant molecules, and thus, have large melting and boiling point.

Element Melting point (K)
Boiling point (K)
Carbon 4373
-
Silicon
1693
3550
Germanium 1218 3123
Tin 505 2896
Lead 600
2024

2. Ionization energy

Ionization energy decreases from Carbon to lead, though not in a regular order. The irregularity in the decrease of these values is due to the fact that the filling of intervening d- orbitals in Ge and Sn and the f- orbitals in Pb, makes it difficult for them to screen the valence electrons effectively.

3. Electronegativity

Carbon is the most electronegative element of the group. There is an irregular decrease in electronegativity as we move down the group. The reason behind this irregularity is because of filling of intervening d and f atomic orbitals.

Carbon Family Uses

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All the elements of carbon are very useful industrially as well as in our day today life.
  1. Graphite, an allotrope of carbon, is used in rockets and missile components.
  2. Silicones are highly stable and non-volatile even on heating. So they find their use in high oil baths and vacuum pumps, etc.
  3. Silicon is the main component in glass industry.
  4. Germanium finds its use as a semiconductor material, with silicon.
  5. Tin and lead finds its use extensively in paint and pigment manufacturing.

Carbon Family Properties

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1. Valency and oxidation state

Carbon family elements are tetravalent in nature, since they have four electrons in their outermost shell. Since the ionization energy of carbon family elements are very high, M4+ , as expected, hardly exists. On account of their low electronegativity, M4- also do not exists.

Some of the compounds of carbon, like carbides have carbon exhibiting a valency of C22-. Silicon does not form tetravalent or divalent cation. The other three elements, Ge, Sn and Pb show both tetra valency and bi valency. Sn2+ and Pb 2+ are more stable and common than Sn4+ and Pb4+.

2. Nature of M2+ and M4+ compounds

The nature of compounds of M2+ and M4+ are predicted by Fajan's rule, which states that : Smaller the cation, the greater is the amount of covalent character in its compounds. Since Sn4+ ion is smaller than Sn2+, the compounds of Sn4+ are covalent in nature while those of Sn2+ are ionic.

In lead too, Pb4+ compounds are covalent while that of the 2+ ions are ionic. Thus, in general, M4+ compounds are covalent, while M2+ ions are ionic. As we move down the group, the ionic characteristics of these compounds, increases.

Chemical Properties of Carbon

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Carbon is a non metal and it forms a lot of covalent compounds.

1. Formation of Hydrides

Carbon combines with hydrogen to form CH4. The hydride formed is covalent in nature.

2. Oxides

There are two oxides of carbon, Carbon monoxide and carbon dioxide. Other oxide, C2O2 also exists.

3. Reaction with halides

Carbon reacts with all halides to form a tetra halide - MX4 . This halide is thermally very stable. Tetra halides of Carbon are the only one which is not hydrolyzed by water, due to the absence of 'd' orbital in carbon.

M + X2 → MX4
4. Formation of acids

Carbon forms both organic and inorganic acids. It forms carbonic acid, H2CO3, the inorganic acid. There is a whole range of acid, with a chemical formula -COOH formed by carbon. These are studied separately in the name of carboxylic acid under organic chemistry.

5. Reaction with alkalies

Carbon does not react with alkalies, though all the other elements in its group are attached by alkalies.

Physical Properties of Carbon

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Though many physical properties of carbon have been discussed above, an important physical property of carbon is catenation.
  • Catenation is the ability to form compounds in which the atoms are linked to each other in chains or rings.
  • Carbon has the greater tendency to combine with other carbon atoms to form quite large carbon chains.
  • Carbon also exists in many allotropic forms, both crystalline and allotropic.
  • graphite and diamond are two important forms. Also, another form of allotrope, Fullerenes, are studied completely as a new branch of chemistry.
Carbon forms a lot of compounds. Some of them , with their method of preparation are as follows.

1. Percarbonic acids and percarbonates


Carbon forms two percarbonic acids which are

(a) Permonocarbonic acid: These are the salts H2CO4 .
    Examples of such salts are Na2CO4, K2CO4, etc.
    Na2CO4 is prepared from the reaction between Na2O2 and Phosgene, COCl2.

2Na2O2 + COCl2 Na2CO4 + 2NaCl + 1/2O2

(b) Perdicarbonates: These are derived from H2C2O6. These are best represented by potassium and sodium salts whose formula are K2C2O6 and Na2C2O6.

Na2C2O6 is prepared by passing F2 in a concentrated solution of Na2CO3 at -13 o C to -16oC.

2Na2CO3 + F2 Na2C2O6 + 2NaF

2. Carbonyl chloride or phosgene


This compound was discovered by John Davy in 1811. It has a chemical formula of COCl2.
It is prepared by the direct combination of equal volumes of CO and Cl2 in the presence of bright sunlight.
CO + Cl2 COCl2

Phosgene is a colorless gas with a penetrating and suffocating odor and is highly poisonous.

3. Carbon disulphide: CS2


This compound was discovered by W. A. Lampadins in 1796. CS2 is manufactured by passing sulfur vapors over hot charcoal or coke.

C + 2S(vapors) CS2
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Uses of Carbon

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  1. Phosgene is used in dyestuff industry, and in warfare.
  2. Carbon di-sulfide is used as a solvent for sulfur, white phosphorus, bromine, etc. It is also used in the manufacture of artificial silk and as an insecticide.
  3. Diamonds, due to their hardness, are used for sawing and cutting marble, cutting glass, etc.
  4. Graphite is used in the manufacture of electrodes and dry cell batteries.
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