Occurrence of Group 16 Elements: Six elements make up Group \(16\) of the extended periodic table: oxygen, sulphur, selenium, tellurium, polonium, and ununhexium. The oxygen family is the name given to this group of elements. Because several metals are found as oxides and sulphides, and a few as selenides and tellurides, Group \(16\) elements are called chalcogens. Because the last differentiating electron is accommodated on the \({\text{np}}\) shell, these are \({\text{p}}\)-block elements. These elements belong to the \({\text{V}}{{\text{I}}^{{\text{th}}}}\) group because they have six electrons in their valence shell.

Occurrence of Group 16 Elements: Overview

In the Earth’s crust, elements in group \(16\) tend to bond with other metals to produce common ores. At \(1\) atm and room temperature, molecular oxygen is a gas. It has no colour, no odour, and no taste. It’s also the most prevalent element in the Earth’s crust and the human body in terms of mass. By weight, oxygen makes approximately \(46.6\) percent of the Earth’s crust. By volume, dry air contains roughly \(21\% \) oxygen. With other elements, oxygen may form extremely strong ionic and covalent bonds.

At room temperature and \(1\) atmosphere pressure, sulphur is solid. It’s usually yellow in colour, tasteless, and odourless. In the Earth’s crust, it is the fifteenth most prevalent element. Sulphur can be found in many different forms in nature, including elemental sulphur, sulphides, sulphates, and organosulfur compounds. Sulphur is unlike any other element in the periodic table in that it may produce a wide range of allotropes. The solid S8 ring is the most common state, as it is the most thermodynamically stable at room temperature.

Sulphur is available in five different gaseous forms \({{\text{S}},{{\text{S}}_2},{{\text{S}}_4},{{\text{S}}_{6,}}}\) and \({{\text{S}}_8}\)). A considerable amount of heat must be provided for sulphur to convert between these compounds. The amount of sulphur in the Earth’s crust, on the other hand, is merely \(0.03 – 0.1\% .\) Sulphur is mostly found as sulphates and sulphides. Sulphates like Gypsum salt \({\text{CaS}}{{\text{O}}_4}.2{{\text{H}}_2}{\text{O}},\) Epsom salt \({\text{MgS}}{{\text{O}}_4},7{{\text{H}}_2}{\text{O}},\) Baryte BaSO4 and sulphides like Galena \({\text{pbS,}}\) Zincblende \({\text{znS,}}\) Copper pyrites \({\text{CuFe}}{{\text{S}}_2}\) are examples. Sulphur traces can also be found in the hydrogen sulphide produced by volcanoes. Organic materials such as eggs, proteins, garlic, onion, mustard, hair, and wool contain sulphur.

Selenium is found in nature as an amorphous red or black solid or as a red or grey crystalline structure. The most stable structure is crystalline. Selenium is rarely found in its basic form in nature; it is usually extracted through a refining process utilising copper. It’s commonly found in soils and plant tissues where the element has bioaccumulated. Sulphide ores contain a trace quantity of selenium and tellurium in the form of metal selenides and tellurides.

Tellurium is an oxygen family metalloid that has a silvery-white colour and a metallic sheen similar to tin at room temperature. Tellurium is a very uncommon element that is most usually found in the form of a gold telluride.

Polonium is a radioactive metal that is extremely rare. It is possible to create around \(33\) distinct isotopes of the element, all of which are radioactive. It has two metallic allotropes and appears in a variety of states. It is easily dissolved in dilute acids. Polonium and Livermorium do not exist as compounds in nature, but they can be synthesised in the lab. Polonium is a decay product of thorium and uranium minerals found in nature.

Electronic Configuration

The following table shows the distribution of electrons in various energy shells of these elements’ atoms:

They all have six electrons in their outermost shell, which is known as the \({{\text{s}}^2}{{\text{p}}^4}\) electrical structure. In the penultimate shell, oxygen has \(2\) electrons, sulphur has 8 electrons, while \({\text{Se,Te}}\) and \({\text{Po}}\) have \(18\) electrons. This is why oxygen is different from the other elements.

Physical State

Others are solids, while oxygen is a gas. The oxygen molecule is diatomic, whereas other elements’ molecules are more complicated. Sulphur, selenium, and tellurium are all \(8\)-atom rings that are staggered. However, sulphur has the highest potential to form \(8\)-atom rings, which decreases as we move down the group. Every sulphur atom in the \({{\text{S}}_8}\) molecule is in a \({\text{s}}{{\text{p}}^3}\) hybridised state, which involves both bonding and nonbonding pairs of electrons.

Atomic and Ionic Radii of Group 16 Elements

The atomic radii of group \(16\) elements are smaller than those of group \(15\) comparable elements. The atomic radii of the elements in this group gradually rise as you progress through the group.
The increased effective nuclear charge with an increase in stronger attraction towards the nucleus causes group \(16\) elements to have smaller atomic radii than group \(15\) elements. The attraction causes the size to shrink. The progressive increase in the number of electron shells from member to member is attributable to the increase in the number of electron shells as you move down the group.

Two electrons are added to an atom during the creation of anions. As a result, the effective nuclear charge decreases, causing the electron to expand. As a result, negative ions are larger than their corresponding atoms. Ionic radii, like atomic radii, gradually grow as you move down the group.

Ionisation Energy

Because the ionisation enthalpies are large, the elements do not readily lose electrons to generate positive ions. As the atomic number increases from \({\text{O}}\) to \({\text{Po,}}\) the tendency to create positive ions decreases, indicating that the metallic nature increases.

Oxidation States

Because the outermost shell configuration is \({\text{n}}{{\text{s}}^2}{\text{n}}{{\text{p}}^4},\) these elements try to gain or share two electrons in order to achieve an inert gas configuration. Except for oxygen fluorides, which are very electronegative, oxygen has a \( – 2\) oxidation state in its compounds, and most metal oxides are ionic and contain oxygen as a negative anion, \({{\text{O}}^{ – 2}}.\) As the electronegativity of the group declines, the tendency to produce a \( – 2\) oxidation state falls. \({\text{S,Se,Te,}}\) and \({\text{Po,}}\) on the other hand, have positive oxidation states. In addition to the \( + 2\) oxidation state, there are also \( + 4\) and \( + 6\) oxidation states. This is due to the availability of \({\text{d}}\)-orbitals in these elements. Oxygen has no \({\text{d}}\)-orbitals and hence cannot show \( + 4\) and \( + 6\) oxidation states, while sulphur can have \(2,4\) or \(6\) unpaired orbitals forming \(2,4\) or \(6\) covalent bonds.
As a result, oxygen is always divalent, while other components can be divalent, tetravalent, or hexavalent. Compounds with a \( + 4\) oxidation state have both oxidising and reducing properties, whereas compounds with a \( + 6\) oxidation state only have oxidising properties.

Uses of Group 16 Elements

The survival of life on Earth depends on the availability of oxygen. Sulphur is required for the digestion of nutrients by both plants and animals. The bulk of selenium is used in the manufacture of glass. Tellurium is utilised in the production of computer discs and other sensitive electrical devices like light sensors. The majority of polonium’s applications are related to its radioactivity. It’s employed in a variety of alpha particle and neutron investigations.

Summary

Six elements make up Group \(16\) or \({\text{VIA}}\) of the extended periodic table: oxygen, sulphur, selenium, tellurium, polonium, and ununhexium. Group \(16\) elements are called chalcogens. Oxygen is the most prevalent element in the Earth’s crust and the human body in terms of mass. Sulphur can be found in many different forms in nature, including elemental sulphur, sulphides, sulphates, and organosulfur compounds. Selenium is found in nature as an amorphous red or black solid or as a red or grey crystalline structure. Tellurium is a very uncommon element that is most usually found in the form of a gold telluride. Polonium is a radioactive metal that is extremely rare.

FAQs on Occurrence of Group 16 Elements

Q.1. Why are 16 group elements called chalcogens?
Ans: Six elements make up Group \(16\) or \({\text{VIA}}\) of the extended periodic table: oxygen, sulphur, selenium, tellurium, polonium, and ununhexium. The oxygen family is the name given to this group of elements. Because several metals are found as oxides and sulphides, and a few as selenides and tellurides, Group \(16\) elements are called chalcogens.

Q.2. What are the uses of group 16 elements?
Ans: The survival of life on Earth depends on the availability of oxygen. Sulphur is required for the digestion of nutrients by both plants and animals. The bulk of selenium is used in the manufacture of glass. Tellurium is utilised in the production of computer discs and other sensitive electrical devices like light sensors. The majority of polonium’s applications are related to its radioactivity. It’s employed in a variety of alpha particle and neutron investigations.

Q.3. Which Is the first element of group 16?
Ans: The first element of group 16 is oxygen.

Q.4. What is the oxidation state of group 16 elements?
Ans: Because the outermost shell configuration is \({\text{n}}{{\text{s}}^2}{\text{n}}{{\text{p}}^4},\) these elements try to gain or share two electrons in order to achieve an inert gas configuration. Except for oxygen fluorides, which are very electronegative, oxygen has a \( – 2\) oxidation state in its compounds, and most metal oxides are ionic and contain oxygen as a dinegative anion, \({{\text{O}}^{ – 2}}.\) As the electronegativity of the group declines, the tendency to produce a \( – 2\) oxidation state falls. \({\text{S,Se,Te,}}\) and \({\text{Po,}}\) on the other hand, have positive oxidation states. In addition to the \( + 2\) oxidation state, there are also \( + 4\) and \( + 6\) oxidation states.

Q.5. Discuss the ionisation energy of group 16 elements.
Ans: Because the ionisation enthalpies are large, the elements do not readily lose electrons to generate positive ions. As the atomic number increases from \({\text{O}}\) to \({\text{Po,}}\) the tendency to create positive ions decreases, indicating that the metallic nature increases.

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