Group 14 Elements (Carbon Family): Properties and Reactions

Pause for a moment and just try to imagine a world where carbon was not there, an element that acts as the backbone for all kinds of organic life. From the carbon dioxide we exhale to the diamond engagement rings that speak of love, carbon surrounds us through the environment. However, carbon is just one member among the interesting elements of group 14 of the periodic table; otherwise, it is known as the carbon family. This group consists of carbon, C, silicon, Si, germanium, Ge, tin, Sn and lead, Pb. Each of these elements, in fact, has a very big impact on the different industries and applications we can have in our daily lives. For example, silicon forms the backbone of the electronics industry, including the one that gets the job done for us with our computers, smartphones, and other devices.

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This Story also Contains

1. Physical Properties of Group 14 Elements - 1
2. Physical Properties of Group 14 Elements -2
3. Relevance and Applications of Group 14 Elements
4. Some Solved Examples
5. Summary

Electronic Configuration
The valence shell electronic configuration of these elements is ns²np². The inner core of the electronic configuration of elements in this group also differs.

Covalent Radius
There is a considerable increase in covalent radius from C to Si, thereafter from Si to Pb a small increase in radius is observed. This is due to the presence of completely filled d and f orbitals in heavier members.

Ionization Enthalpy
The first ionization enthalpy of group 14 members is higher than the corresponding members of group 13. The influence of inner core electrons is also visible here. In general, the ionization enthalpy decreases down the group. The small decrease in $\Delta_{\mathrm{i}} \mathrm{H}$ from Si to Ge to Sn and a slight increase in $\Delta_{\mathrm{i}} \mathrm{H}$ from Sn to Pb is the consequence of poor shielding effect of intervening d and f orbitals and increase in size of the atom.

Electronegativity
Due to the small size, the elements of this group are slightly more electronegative than group 13 elements. The electronegativity values for elements from Si to Pb are almost the same.

Physical Properties of Group 14 Elements - 1

The elements of Group 14 range from non-metal to post-transition metal; this means they do show a qualitative variation in the physical properties down the group. It is because of the addition of electron shells that the atomic radius increases from carbon to lead. A small atomic radius for carbon can give strong covalent bonds, resulting in the hardest natural substance, the diamond, and also one that is soft, graphite. Silicon and germanium are metalloids. They have some of the typical properties of metals and some of the typical properties of nonmetals—moderate electrical conductivities, and they are quite thermally stable. Tin and lead are metals that show common trends, they are malleable and ductile. It conforms to the general decrease in melting and boiling points down the group, except carbon, with a much higher value as a consequence of the very strong covalent bonds within the network structures.

Allotropy
The ability of an element to exist in more than one physical form is called allotropy. All the elements of this group except Pb exhibit allotropy. Carbon has three allotropes i.e, diamond, graphite, and fullerene

Valency
All the elements of this group show tetravalency as they have 4 electrons in their valence shell.

Atomic and Ionic radii
As we move down the group, the radius of these elements increases.

Multiple Bonding
Carbon forms p-p bonding with itself and with S, N, and O. While the other elements of this group form p-d bonding as they have a vacant d-orbital while carbon does not have.

Physical Properties of Group 14 Elements -2

One of the interesting physical properties related to carbon is allotropy. It has a number of allotropes resulting, which include diamond, graphite, graphene, or fullerenes. All these allotropes commonly depict customary physical characteristics of carbon: diamond, for one, being very hard, depicts a good conduction of heat; graphite has lubricating and electrical-conducting properties. In fact, silicon comes in many crystalline forms, the best known being the diamond cubic structure. The bandgap of silicon makes this an extremely important factor for semiconductor devices. Germanium is also somewhat like silicon, although less abundant and not quite so versatile in its uses either. It finds applications in specialized electronic devices. The metal tin exists in two allotropes: white tin, a metallic, ductile conductor of electricity, and gray tin, a brittle, non-metallic semiconductor. Finally, lead is the densest and most metallic member of this family. It is a very malleable metal with good resistance to corrosion and, therefore, finds applications in many kinds of industries.

Hydrides

• All the members of this group form covalent hydrides.
• Hydrides of carbon are called hydrocarbons.
• Hydrides of Si and Ge are known as silanes and germanes.
• The thermal stability of hydrides decreases down the group.
• Reducing character increases down the group

Relevance and Applications of Group 14 Elements

The carbon family elements play a very meaningful role in many spheres. As far as organic chemistry is concerned, carbon goes without saying that it makes the basic constituent of organic compounds and, therefore, the very backbone of life in the form of organic chemistry. Industrially, the allotropes of carbon have a magnitude of applications, from the creation of tools to lubricants and electrodes, especially because of the semiconductor property that is characteristic of silicon and which, because of its allotropic nature, makes this material the backbone of the electronics industry and of the basic components for the production of integrated circuits and solar cells.

Halides

These elements can form halides of the formula MX₂ and MX₄ (where X = F, Cl, Br, I). Except carbon, all other members react directly with halogen under a suitable condition to make halides. Most of the MX₄ are covalent in nature. The central metal atom in these halides undergoes sp³ hybridization and the molecule is tetrahedral in shape. Exceptions are SnF₄ and PbF₄, which are ionic in nature. PbI₄ does not exist because Pb—I bond initially formed during the reaction does not release enough energy to unpair 6s² electrons and excite one of them to a higher orbital to have four unpaired electrons around lead atom. Heavier members Ge to Pb are able to make halides of formula MX₂. The stability of dihalides increases down the group. Considering the thermal and chemical stability, GeX₄ is more stable than GeX₂, whereas PbX₂ is more stable than PbX₄. Except for CCl₄, other tetrachlorides are easily hydrolyzed by water because the central atom can accommodate the lone pair of electrons from the oxygen atom of a water molecule in d orbital.

All members when heated in oxygen form oxides. There are mainly two types of oxides, i.e., monoxide and dioxide of formula MO and MO₂ respectively. SiO only exists at high temperatures. Oxides in higher oxidation states of elements are generally more acidic than those in lower oxidation states. The dioxides — CO₂, SiO_2, and GeO₂ are acidic, whereas SnO₂ and PbO₂ are amphoteric in nature. Among monoxides, CO is neutral, GeO is distinctly acidic whereas SnO and PbO are amphoteric.

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Some Solved Examples

Example 1
Question: Which of the following pairs have equal electronegativity?
1) C and Si
2) Si and Ge
3) Ge and Sn
4) (2) and (3) both

Solution: The electronegativity values for Group 14 elements decrease from carbon to lead, but not in a regular manner due to the filling of d and f orbitals. The electronegativity of carbon (C) is 2.5, while silicon (Si), germanium (Ge), and tin (Sn) each have an electronegativity of 1.8. Therefore, both Si and Ge and Ge and Sn have equal electronegativity values. Hence, the correct answer is option (4).

Example 2
Question: 'X' melts at a low temperature and is a bad conductor of electricity in both liquid and solid states. X is:
1) Carbon tetrachloride
2) Silicon carbide
3) Mercury
4) Zinc sulphide

Solution: Carbon tetrachloride (CCl4) is a non-polar compound with a melting point of −22.92°C. It is a poor conductor of electricity in both liquid and solid states because it is a non-electrolyte and a covalent compound, meaning it consists of molecules with no charge separation. Hence, the correct answer is option (1).

Example 3
Question: The melting point of silicon is:
1) Higher than B
2) Lower than Al
3) Higher than C
4) Lower than C

Solution: The melting points of the elements in Group 14 vary. For example, boron (B) has a melting point of 2553 K, aluminum (Al) has a melting point of 933 K, carbon (C) has a melting point of 4373 K, and silicon (Si) has a melting point of 1693 K. From this data, we see that silicon has a lower melting point than carbon. Hence, the correct answer is option (4).

Summary

The elements of Group 14 that fall in the carbon family vary over a diverse set of variations in the physical properties down the group. From the covalent bond of carbon to allotropy, from semiconductor features of silicon and germanium to metallic properties for tin and lead, these elements would all be essential in application. Generally, it is their divergent properties that would hold a central position in aspects of electronics, material science, chemistry, and industry. Knowing the physical properties and the possibilities of usage for an element of group 14, one realizes how important and helpful they are from an academic and also practical point of view.