The group 16 elements of modern periodic table consist of 5 elements oxygen, sulphur, selenium, tellurium and polonium. The elements in this group are also known as the chalcogens or the ore-forming elements because a large number of elements can be extracted from the sulphide or oxide ores.
Oxygen is abundantly found on the earth. Estimating the proportions of different types of atoms found in the universe, oxygen was claimed as the fourth abundant element after hydrogen, helium, and neon. It constitutes about 89% of water, 46% of the earth crust and 20 % of the air.
|Period||Element||Symbol||Atomic Number||Electronic Configuration|
|2||Oxygen||O||8||[He] 2s2 2p4|
|3||Sulphur||S||16||[Ne] 3s2 3p4|
|4||Selenium||Se||34||[Ar] 3d10 4s2 4p4|
|5||Tellurium||Te||52||[Kr] 4d10 5s2 5p4|
|6||Polonium||Po||84||[Xe]4f14 5d10 6s2 6p4|
The chemical symbol for oxygen is given as O. It is a colourless and odorless gas used in respiration process by humans, which is converted into carbon dioxide. Oxygen exists as a diatomic molecule (O2). Oxygen is also found as a triatomic molecule (O3) in traces, it is known as ozone. Oxygen combines readily with many elements. During the combination with some elements, the evolution of heat energy takes place, this process is known as combustion.
Sulphur is denoted by the symbol S. It is a non-metal which ranks ninth on the basis of cosmic abundance. About 1 atom in every 20,000-30,000 atoms is a sulphur atom. Sulphur is found in the combined state as well as in free state. About 0.09 % of sulphur is found in seawater in the form of sulphates. Meteorite contains 12 % of sulphur, a large amount of sulphur is found from the underground deposits of pure sulphur present in dome-like structures. Here sulphur is formed by the action of anaerobic bacteria on the sulphate minerals such as gypsum.
Selenium is rarer than oxygen or sulphur. It is found in the free state as well as in the combined state with heavy metals (as lead, silver, or mercury) in a few minerals. Grey metallic form of the selenium is the most stable form of the element under normal conditions.
Tellurium is a chemical element having atomic number 52 and has the properties between metals and non-metals. It is one of the rarest stable elements found in the earth’s crust. It is often found in free state and in compounds with elements such as copper, lead, silver or gold.
It is the rarest element among the group 16 elements. It is a radioactive element. Polonium is sometimes used in scientific applications for alpha radiation.
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