Atomic and Physical Properties of Group \(16\) Elements: The elements are classified into four blocks in the long form of the periodic table: \({\rm{s}},{\rm{p}},{\rm{d}},\) and \({\rm{f,}}\) depending on the subshell into which the last electron enters.

The elements in the periodic table’s \({\rm{s}}\) and \({\rm{p}}\) blocks are known as representative elements or main group elements. They are divided into two parts – range from group \(1\) to \(2\) and from group \(13\) to \(18\). Elements in groups \(1\) and \(2\) belong to the \({\rm{s}}\)-block, while elements in groups \(13\) to \(18\) belong to the \({\rm{p}}\)-block.

 In this article, we will study all about the atomic and physical properties of a group in the \({\rm{p}}\)-block, that is group \(16\)- Oxygen family.

Group 16 Elements

The \({\rm{p}}\)-block elements are placed on the right-hand side of the periodic table from groups \(13\) to \(18\).

Group \(16\) includes five elements which are oxygen \({\rm{(O)}}\), sulphur \({\rm{(S)}}\), selenium \({\rm{(Se)}}\), tellurium \({\rm{(Te)}}\) and polonium \({\rm{(Po)}}\).

These are known as the oxygen family, after the first member of the group. Because many metal ores occur as oxides and sulphides, the first four elements of this group are collectively known as chalcogens, which means ore-forming elements.

Occurrence of Group 16 Elements

Oxygen is the most abundant element available in nature. It contributes \(20.946\) percent of the volume of air and \({\rm{46}}{\rm{.6 \% }}\) of the earth’s crust by mass as silicates and other compounds such as carbonates, oxides, and sulphates.

Photosynthesis in plants provides the vast majority of the oxygen in the air. It can also be found as ozone.
Sulphur is the sixteenth most abundant element. Ores contain sulphur in their combined state.

Gypsum \({\rm{CaS}}{{\rm{O}}_4}.2{{\rm{H}}_2}{\rm{O}}\), Epsom salt \({\rm{MgS}}{{\rm{O}}_4}.7{{\rm{H}}_2}{\rm{O}}\), and barytes \({\rm{BaS}}{{\rm{O}}_4}\) are all examples of sulphate ores.

Galena \(({\rm{PbS}})\), zinc blende \(({\rm{ZnS}})\), and copper pyrites \(\left( {{\rm{CuFe}}{{\rm{S}}_2}} \right)\) are examples of sulphide ores.

Sulphur can also be found in a variety of organic substances, including mustard, eggs, seeds, onion, wool, garlic, and hair.

Metal selenides and tellurides of selenium and tellurium are found in sulphide ores.

Polonium is a naturally occurring radioactive element.

Trends in Group \(16\) Elements

The trends in Group 16 are explained below:

Electronic Configuration of Group 16 Elements

The elements in Group \(16\) have \(6\) electrons in their valence shell and have the following general electronic configuration: \({\rm{n}}{{\rm{s}}^2}{\rm{n}}{{\rm{p}}^4}\).

Atomic and Ionic Radii of Group 16 Elements

The atomic and ionic radii of this group’s elements are smaller than those of group \({15^\prime }{\rm{s}}\) corresponding elements. As one moves down the group, the atomic and ionic radii of the elements increase.

Group 16 Elements Ionisation Enthalpy

The ionization enthalpy of this group’s elements is smaller than those of group \({15^\prime }{\rm{s}}\) corresponding elements. As one moves down the group, the ionization enthalpies of the elements decrease.

Members of group \(16\) have higher second ionisation enthalpies than members of group \(15\). This is due to the fact that after the first electron is removed, the second electron must be removed from a more symmetrical half-filled configuration, which is more stable.

Electron Gain Enthalpy of Group 16 Elements

The electron gain enthalpy decreases as the atomic size increases down the group. The electron gain enthalpy of oxygen is less negative than that of sulphur. Because of its compact nature, oxygen experiences more repulsion between the electrons already present and the incoming electron. Because of these electron-electron repulsions, the oxygen atom has a lower proclivity to accept the extra electron than the sulphur atom.

Melting and Boiling Points of Group 16 Elements

The melting and boiling points increase as the atomic size increases from oxygen to tellurium.
The vast difference in the melting and boiling points observed in the case of oxygen and sulphur may be because oxygen exists as a diatomic molecule and sulphur as a polyatomic molecule.

Group 16 Elements Electronegativity

The elements of group \(16\) have higher electronegativity values than the elements of group \(15\). The second most electronegative element is oxygen, with fluorine being the first. As one moves down the group, the electronegativity decreases. The increase in atomic radii of elements causes a decrease in electronegativity.

Metallic Character of Group 16 Elements

Metallic character increases down the group. The first two elements- oxygen and sulphur are non-metals. Selenium and tellurium being the metalloid, and polonium can be classified as a metal.

Catenation of Group 16 Elements

The ability of an atom to form a long chain structure by forming bonds with identical atoms is called catenation. Only sulphur has a high tendency for catenation in this group. To a lesser extent, oxygen exhibits this tendency as well.

Elemental State of Group 16 Elements

Oxygen exists in the form of a diatomic molecule. It exists in the form of a gas. There is a \({\rm{p\pi }} – {\rm{p\pi }}\) overlap between two oxygen atoms in an oxygen molecule, forming a double bond, \({\rm{O}} = {\rm{O}}\). Because the intermolecular forces in oxygen are weaker than Van der Waals forces, oxygen exists as a gas.

The remaining members of the family do not form stable \({\rm{p\pi }} – {\rm{p\pi }}\) bonds and do not exist as diatomic molecules. The other atoms are connected by single bonds, resulting in polyatomic complex molecules.

Allotropy of Group 16 Elements

All the elements of this group exhibit allotropes.

1. Oxygen exists as dioxygen and ozone.
2. Sulphur exists as yellow ortho-rhombic, \({\rm{\alpha }}\) and \({\rm{\beta }}\) monoclinic forms.
3. Selenium exists as eight allotropes, out of which three are red monoclinic forms containing \({\rm{S}}{{\rm{e}}_8}\) rings. Grey-hexagonal metallic selenium with polymeric helical chains is the thermodynamically stable form. The element is found in the form of common amorphous black selenium. Grey selenium is the only selenium allotrope that conducts electricity.
4. Tellurium only has one crystalline form with a chain structure similar to grey selenium.

Oxidation States of Group 16 Elements

The group \(16\) elements have an outer shell configuration of \({\rm{n}}{{\rm{s}}^2}{\rm{n}}{{\rm{p}}^4}\); they can achieve noble gas configuration by gaining two electrons, forming \({{\rm{M}}^{ – 2}}\) ion, or by sharing two electrons, forming two covalent bonds. As a result, these elements represent both negative and positive oxidation states. The elements in group \(16\) have regular oxidation states of \(-2, +2, +4,\) and \(+6\).

Anomalous Behaviour of Oxygen

In general, the properties of the principal element of any group differ from those of the other elements. Oxygen’s properties differ from those of other elements of the group. Oxygen’s exceptional properties are attributed Due to the following:

1. Its small nuclear size,
2. High ionisation enthalpy or electronegativity,
3. Lack of d-orbitals.

Points of Difference between Oxygen and Other Members:

1. Others are complex solids, whereas oxygen is a diatomic gas.
2. Because of its high electronegativity, oxygen is highly nonmetallic.
3. The di-negative anions of other members are less common; oxygen is easily converted to \({{\rm{O}}^{2 – }}\) ion.
4. iv. The oxygen molecule is highly stable because the two atoms are held together by a relatively strong multiple bonds with a high bond energy. As a result, ordinary oxygen is inactive under normal conditions.
5. In its gaseous, liquid, and solid states, the oxygen molecule is paramagnetic and has two unpaired electrons. The rest are diamagnetic.

Uses of Group 16 Elements

Some of the applications of group \(16\) elements are discussed as follows-

1. The production of steel, plastics, and textiles, brazing, welding, and cutting of steels and other metals, rocket propellant, oxygen therapy, and life support systems in aircraft, submarines, spaceflight, and diving are all common uses of oxygen.
2. Elemental sulphur is used in the manufacture of black gunpowder, matches, and fireworks, as well as in the vulcanization of rubber and as a fungicide, insecticide, and fumigant.
3. Selenium is used in the production of pigments for ceramics, paint, and plastics. It has applications in photocells, solar cells, and photocopiers.
4. Tellurium has been used in the vulcanization of rubber, the tinting of glass and ceramics, solar cells, rewritable CDs and DVDs, and as an oil refining catalyst.
5. Polonium has only a few uses, all of which are related to its radioactivity: heaters in space probes, antistatic devices, neutron and alpha particle sources, and poison.

Summary

In this article, we studied that in the long form of the periodic table, the \({16^{{\rm{th}}}}\) vertical column or VIA group elements are oxygen, sulphur, selenium, tellurium, and polonium. The first four elements of the group are referred to as chalcogens or ore-forming elements. We studied the general trends along with the group as well as the anomalous behavior of oxygen.

FAQs on Group 16 Elements

Q.1. What are the atomic and physical properties of group 16 elements?
Ans: Some of the physical properties of group \(15\) are as follows:
i. The atomic and ionic radii increase as we go down the group-\(16\) from oxygen to polonium.
ii. The ionization enthalpies of the elements decrease on moving down the group.
iii. The electron gain enthalpy decreases as the atom’s size decrease down the group, but oxygen has the least negative electron gain enthalpy.
iv. The melting and boiling points increase as the atomic size increases from oxygen to tellurium.
v. The first two elements- oxygen and sulphur are non-metals. Selenium and tellurium being the metalloid, and polonium can be classified as a metal.
vi. The elements in group \(16\) have regular oxidation states of \(-2, +2, +4,\) and \(+6\).

Q.2. What is special about group 16 on the periodic table?
Ans: The special thing about group \(16\) is that the first four elements are called chalcogens, which means ore-forming elements.

Q.3. What are the uses of group 16 elements?
Ans: Some of the uses of group \(16\) elements are as follows:
i. The production of steel, plastics, and textiles, as well as brazing, welding, and cutting of steels and other metals, all require the use of oxygen.
ii. Sulfur is used in the production of black gunpowder, matches, and fireworks.
iii. Selenium is used in the production of pigments for ceramics, paint, and plastics. It has applications in photocells, solar cells, and photocopiers.
iv. Tellurium has been used in the vulcanization of rubber, the tinting of glass and ceramics, solar cells, rewritable CDs and DVDs, and as an oil refining catalyst.
v. Polonium is only used in a few applications, including space probe heaters, antistatic devices, neutron and alpha particle sources, and poison.

Q.4. What are group 16 elements called?
Ans: Group \(16\) is known as the oxygen family, after the first member of the group. Because many metal ores occur as oxides and sulphides, the first four elements of this group are collectively known as chalcogens, which means ore-forming elements.

Q.5. Name the elements present in group 16?
Ans: Group \(16\) includes five elements which are oxygen \({\rm{(O)}}\), sulphur \({\rm{(S)}}\), selenium \({\rm{(Se)}}\), tellurium \({\rm{(Te)}}\) and polonium \({\rm{(Po)}}\).