It is interesting to note that certain elements behave like oxygen. In other words, these elements exhibit properties and trends similar to those of oxygen. The members of such a collective group are known as Group 16 elements. Let us see the similarities between oxygen and the other members of this group. We shall also understand why oxygen is an important member of this group.
For convenience sake, we can call this group as the chalcogen family. This family consists of elements found in group 16 of the periodic table. It is essential to remember that periodic tables are an arrangement of elements with similar properties. The chalcogen family is placed under the oxygen classification. Now, these chalcogens are considered as the leading group 16 elements. The elements in this group are – oxygen, sulphur, selenium, tellurium, and polonium. Ref Fig.1.
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Chalcogens is the name given to periodic table group 16 elements or V1. This group consists of oxygen, sulphur, selenium, tellurium, and polonium. When we call them elements, it is essential to note that oxygen is a gas while other group members are solids. Oxygen and Sulphur are available in pure form while other elements occur as ions in metal ores. O and S form oxides and sulphides.
All elements of this group have isotopes with varying stability. The elements of this group and their compounds vary in their toxicity. O and S are essential to all forms of life. Compounds of selenium, tellurium, and polonium can be hazardous. Selenium is a trace element and can cause disorders. Tellurium compounds have not been known to cause a human fatality. Polonium and its compounds are radioactive, extremely toxic, and need to be handled with care.
The chalcogens or the oxygen group is placed in column 16 of the periodic table (ref fig 1). It has elements of oxygen, sulphur, selenium, tellurium, and polonium. You may find one more element, livermorium. The chemical symbols for these elements are- O, S, Se, Te, PO, and Lv. The first four elements of this group are known as chalcogens or ore-forming elements. The reason is that a majority of metal ores found in the Earth’s crust are sulphides or oxides.
You know that oxygen is the most freely found element in nature. It forms 20.946 percent of air and 46.6 percent of the world’s mass generally in the form of silicates, carbonates, oxides and sulphates. We need oxygen to breathe.
All group 16 elements are closely related to human life.
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Oxygen – chemical notation of oxygen is O. It is a colourless and odourless gas. We inhale oxygen and exhale carbon dioxide. Trees exhale oxygen. Oxygen combines with many elements to form their oxides.
Sulphur – the chemical symbol for sulphur is S. It is found in combined as well as the isolated state. In seawater, the percentage of sulphur is 0.09. A large amount of sulphur is found in underground deposits.
Selenium is a rare element. Selenium is found in free as well as in combination with heavy metals such as lead, silver, and mercury in some minerals. Selenium is most stable in grey metallic form.
Tellurium is an element that has properties between metals and non-metals. It is one of the rarest stable elements found on earth. It is located in compounds with copper, lead, silver, and gold. Tellurium is also found in a free state.
Polonium is a radioactive element or isotope in the group 16 elements. It has scientific applications for alpha radiations as it is a radioactive element. It is also a rare element.
1. What is a Periodic Table?
A periodic table is a table in which elements get an arrangement in order of increasing atomic number. Elements that have similar properties are arranged in the same column (group), and elements with the same number of electrons are arranged in the same row (period). In simple words, a periodic table is a graphical collection of element data. It is a listing of chemical elements in order of increasing atomic number - the protons in an atom of an element. You will find 18 groups and 7 periods in the modern periodic table. All the elements that appear in the same group exhibit similar physical and chemical properties.
2. What are Chalcogens?
The term chalcogen was first in use by Wilhelm Blitz and Werner Fischer, members of a research group at the University of Hannover in Germany. The two named this ‘particular group’ as chalcogens in 1932. The word chalcogen was derived from the Greek word chalcos meaning ore formers as in copper ores. However, chalcogen has nothing to do with copper, so it means ‘ore former’. As you already know, that oxygen and sulphur form oxides and sulphide ores. The name chalcogens relate to the group 16 oxygen family. Their compounds are known as chalcogenides. The name chalcogen became popular as it is similar to the names of group 17 – the halogens, meaning, salt formers.