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Group-14 elements (IVB) in the periodic table include carbon (C), silicon (Si), germanium, tin (Sn), and lead (Pb) with the atomic number 6, 14, 32, 50, 82. The first two elements in the carbon family occupy a special position in our life. Carbon is the key chemical element of all living organisms forms a large number of organic and inorganic compounds. Silicon is the second most abundant element after oxygen in the earth's crust. Silicon compounds like stones, sands, and clays are the principal building materials in our civilization.

Properties of Group-14 Elements

The chemistry of the group 14 elements follows from their electronic configuration although the references in properties between carbon and silicon are rather wide.

The metallic character of group 14 elements increasing with the increasing atomic number. Therefore, carbon and silicon are typically nonmetals but the metallic properties increasing from germanium to lead. The sum of four ionization energy is exorbitantly high and cannot form an M⁺⁴ cation. Therefore, in most cases, the elements attaining noble gas configuration by forming four single covalent bonding with sp³ hybridization. The formation of multiple chemical bonding decreases from carbon to silicon atom.

The group-14 elements, carbon has several types of allotropic forms, only diamond and graphite are common among them. The four other rare and poorly understood forms are beta-graphite, Lonsdsdaleite, or hexagonal diamond, chaoite, and carbon-VI. Silicon and germanium diamonds type cubic crystal lattice with Si-Si bond distance 235 pm. Tin has two allotropic forms like alpha-tin and beta-tin but lead exists only in a cubic closed paced metallic crystal lattice with a density of 11.34 g cm^-3.

Group-16 elements or Group-VIB contains chemical elements like oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium with the atomic number 8, 16, 34, 52, 84. Oxygen is the most abundant element and makes up to 47 percent of the earth's crust in the form of oxides and oxoacids. It supports the respiration of the animal body and essential for human life. Sulfur occurs in the native state and metal sulfides like pyrites (FeS₂), galena (PbS), zinc blended (ZnS), and metal sulfate like gypsum (CaSO₄, 2H₂O). It makes up to 0.04 to 0.03 percent of the earth's crust. Selenium and tellurium contain fewer quantities in sulfide ores. Polonium was discovered by scientist Curies from the radioactive materials pitchblende in 1898. It also from the radioactive decay of radium.

Properties of Group-16 Elements

The elements of group 16 are collectively called chalcogen from their natural association with copper (chalcos). Oxygen has two allotopic forms like dioxygen (O₂) and ozone (O₃). Ozone is formed in the upper atmosphere by the action of solar UV radiation on oxygen. The ozone layers protect the earth from harmful electromagnetic radiation coming from the sun. Nitrogen oxide and chlorofluorocarbons destroy the ozone layers. The element sulfur forms a large number of allotropes containing puckered rings with 6 to 20 atoms or chains. Common rhombic and liquid sulfur contains an S₈ ring with a melting point of 115°C. The trend in various properties among the group members parallels those observed in previous groups. The first member of Group-16 like the oxygen has a strong tendency to form a chemical bond or pi-bond with p-p orbitals and a strong hydrogen bonding.

Nitrogen in Periodic Table Elements

Nitrogen atomic number 7 and symbol N is the chemical element of Group 15 of the periodic table occurs as the diatomic gas dinitrogen N₂ with no allotropic forms. The elements of this group like nitrogen, phosphorus, arsenic, antimony, and bismuth are collectively called pnictogen or pnicogen from the greek word choking. The element nitrogen and phosphorus are essential constituents of the living system used mainly for the manufacturing of fertilizer. The heavier member of the group, particularly arsenic is extremely toxic and causes water pollution.

Chemistry of Nitrogen

The chemistry of the element is very interesting. The remarkable tendency of catenation is observed in carbon and practically disappears in nitrogen. The importance of p-p pi-bonding increases with the increasing electronegativity of the atom. The electronic configuration of nitrogen is 3s² 3p³ with two paired electrons in the s-orbital and one unpaired electron in three p-orbitals. The electronic configuration suggests that nitrogen is closer to the next noble gas neon than the presiding noble gas helium. If we assuming the +5 cationic configuration by losing all the five outer electrons is just impossible. A huge amount of energy is required for this purpose. The sum of five ionization energy cannot be compensated by the gain of lattice energy by ionic bonding. Therefore nitrogen formed chemical compounds in +5 oxidation states are covalent compounds. The first ionization energy fall from nitrogen to bismuth is slow but metallic character along with the group steadily increases.

Nitrogen halides are restricted up to only the trihalides but phosphorus has pentahalides in addition to the trihalides due to the presence of vacant d-orbital in phosphorus atom. The d-orbitals of phosphorus can utilize to form pentavalent trigonal bipyramidal PCl₅ with sp³d hybridization.

Uses

Nitrogen is the essential chemical constituent of plants and animals used widely to provide an inert atmosphere in metallurgy and in various chemical industries like the iron and steel industry or petrochemical industry. Liquid nitrogen is used as a refrigerant in low-temperature matching and grinding rubber or rubber-like substance, preservation of biological specimens.

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Cobalt in Periodic Table

Cobalt (Co) is a silvery-gray ferromagnetic transition metal of Group 9 (VIIIB) of the periodic table element that is used in making alloys, and large quantities of its compounds. These compounds are used for making glass and ceramic materials.

The hexagonal crystal lattice, cobalt has the chemical symbol Co, atomic number 27. Some physical properties of cobalt like melting point, boiling point, density, atomic weight, and electronic configuration of the metal are given below the picture.

Properties of Cobalt

Occurrence and uses

Cobalt is less common among the first transition metals except for scandium. It is the thirtieth most abundant element of all known elements that occurs mainly with nickel and arsenic. The principal minerals of cobalt are arsenides and sulfides like smaltite, CoAs₂, erythrite, and Co₃(AsO₄)₂.

Besides arsenic, sulfur, and iron, the minerals contain 4 to 10 percent of nickel, and a varying amount of silver, copper, and lead. South Africa and Canada are the main producers of cobalt and small reserves of metal are also present in Australia and Russian countries.

• Before the 19th century, large quantities of cobalt compounds are used in glass and ceramic industries but presently it is used in different fields like alloy or battery making and chemical catalysts.
• Cobalt compounds or blue pigments are used in glass and ceramic industries due to their artistic color.

History of Vanadium

Vanadium is the chemical element of group 15 of the periodic table elements. The presence of the new element in some Mexican lead ore was first isolated by A del Rio in 1801 who named it erythronium (Greek erythros meaning red). The matter subsided when the mineral was wrongly thought to be basic lead chromate.

In 1830, Sefstrom found the same new element in Swedish iron ore, the element gave the compound a variety of brilliant colors. So he named it Vanadium after the Scandinavian Goddess of beauty, Vanadis.

In 1831, Wohler showed that vanadium and erythronium were the same elements. Berzelius prepared a number of its compounds, the metal was first isolated by Roscoe in 1867 by reduction of VCl₂. 

Physical Properties and Uses

• Vanadium is a hard, silvery-grey, malleable transition metal or chemical element with the symbol V, atomic number 23.
• It is a metal that is rarely found in nature but once isolated artificially and formed of an oxide layer.
• It is a good electrical conductor and an effective thermal insulator.
• Pure metal is soft, malleable, and ductile but impurities make it hard and brittle.
• The melting point and density of vanadium are higher than those of titanium showing additional involvement of d electron in chemical bonding.
• Naturally, occurring vanadium contains one stable isotope, ⁵¹V, and one radioactive isotope ⁵⁰V.
• The chemistry of vanadium is going mostly to four adjacent oxidation states or oxidation number like 2–5.