Modern Periodic Table
The modern periodic table created by Dmitri Mendeleev arranges all the elements known to man in a systematic order. The elements are arranged according to the ascending order of their atomic numbers. Since no two elements have the same atomic number, every element occupies a predetermined spot on the table. Elements with similar electronic configurations exhibit similar properties and are hence categorized into one group. One curious feature of the modern periodic table is, it is arranged in such a way that you notice a general trend in the properties of elements in one group. In CBSE Class 11 Chemistry, groups 13 and 14 of the p-block of periodic table were taught to you. Let’s now explore Group 15 – Pnicogens aka Nitrogen group.
p Block elements: Group 15
The Group 15 in the Periodic table consists of 5 naturally available elements and one that has been manufactured by us; namely Nitrogen, Phosphorus, Arsenic, Antimony and Bismuth. The last one being Ununpentium, it is a synthetic superheavy element, which has been observed only in the laboratory and it is very unstable. Antimony was the first of the pnictogens to be obtained in elemental form and recognized as an element. The ancient Egyptians used finely ground Antimony Sulphide for eye makeup (kohl). Arsenic has been known to physicians and professional assassins since ancient Greece. Bismuth has a chequered history because scientists kept confusing it with other elements such as lead, tin, antimony due to similar appearance. It was finally isolated in the 15th century.
Phosphorus was discovered in 1669 by a German alchemist who distilled the pure element out of putrefied human urine. It was named after its unusual property of glowing in the dark (phos= Light, phoros= bringing). Phosphorus occurs in minerals such as Ca9(PO4)6.CaF2 (Fluorapatite) and is also present in bones as well as living cells. Phosphorus was essential to us to make matchsticks, especially during wartime. Despite its abundance, Nitrogen was the last to be obtained in its pure form. It’s a very inert gas and reacts with a very few reactants. In the Earth’s crust, it occurs as Sodium Nitrate aka Chile saltpetre (NaNO3) and Potassium Nitrate (KNO3). About 90% of the Nitrogen produced is used to provide an inert atmosphere for oxygen-sensitive reactions.
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