Group 16 Elements (Oxygen Family): Properties and Reaction

Imagine such a world without oxygen. There would thus be no breathing and as such life would disappear. There are some members of elements in Group 16 of the periodic table key to life in which oxygen belongs. This group comprises the members thus namely oxygen, sulphur, selenium, tellurium, and polonium. These elements are very vital in various natural processes and industrial applications.

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This Story also Contains

1. Details of some atomic and physical properties of Group 16 elements can be found below:
2. Chemical Properties – 1
3. Chemical Properties - 2
4. Applications and Importance
5. Some Solved Examples
6. Summary

Details of some atomic and physical properties of Group 16 elements can be found below:

Chemical Properties – 1

Elements of Group 16 – An Overview

Group 16 members have six valence electrons, and these valence electrons account for their chemical properties and reactivity. The group consists of oxygen, sulphur, selenium, tellurium, and polonium. It follows that changes in trend from non-metal to metal with these elements—in this group, graduations of metalloids and finally metals—are gradual. They inherently combine with other elements to get a wide variation of oxidation series, ranging from –2 to +6, and this is why such a broad range of chemical behaviours and applications are noted.

Oxidation states and trends in chemical reactivity
The elements of Group 16 exhibit several oxidation states. The stability of the -2 oxidation state decreases down the group. Polonium hardly shows a –2 oxidation state. Since the electronegativity of oxygen is very high, it shows only a negative oxidation state as –2 except in the case of OF₂ where its oxidation state is +2. Other elements of the group exhibit +2, +4, +6 oxidation states but +4 and +6 are more common. Sulphur, selenium, and tellurium usually show a +4 oxidation state in their compounds with oxygen and +6 with fluorine. The stability of the +6 oxidation state decreases down the group and the stability of the +4 oxidation state increases (inert pair effect). Bonding in +4 and +6 oxidation states is primarily covalent.

Chemical Properties - 2

Different Aspects of Chemical Behaviour

The chemical properties of Group 16 elements include electronegativity, ionization energy, and reactivity. Oxygen is a highly electronegative element and forms strong covalent bonds with atoms of most other elements; hence, oxygen is easily the common constituent of most organic molecules, including H₂O. Sulphur is much less electronegative and forms sulphuric acid, H₂SO₄, and sulphides such as FeS₂. The metalloids selenium and tellurium probably exhibit intermediate kinds of behaviour and form compounds such as selenides and tellurides. Then there is polonium, a very rare and very strongly radioactive element; the only likely concern would be nuclear science. For the most part, this category of elements falls down the list, and reactivity decreases with an increase in atomic size and a decrease in ionization energy.

Reactivity with hydrogen: All the elements of Group 16 form hydrides of the type H₂E (E=O, S, Se, Te, Po). Their acidic character increases from H₂O to H₂Te. The increase in acidic character can be explained in terms of decrease in bond enthalpy for the dissociation of H–E bond down the group. Owing to the decrease in enthalpy for the dissociation of the H–E bond down the group, the thermal stability of hydrides also decreases from H₂O to H₂Po. All the hydrides except water possess reducing properties and this character increases from H₂S to H₂Te.

• Reactivity with oxygen: All these elements form oxides of the EO₂ and EO₃ types where E = S, Se, Te, or Po. Ozone (O₃) and sulphur dioxide (SO₂) are gases while selenium dioxide (SeO₂) is solid. The reducing property of dioxide decreases from SO₂ to TeO₂; SO₂ is reducing while TeO₂ is an oxidizing agent. Besides EO₂ type, sulphur, selenium, and tellurium also form EO₃ type oxides (SO₃, SeO₃, TeO₃). Both types of oxides are acidic in nature

• Reactivity towards the halogens: Elements of Group 16 form a large number of halides of the type EX₆, EX_4, and EX₂ where E is an element of the group and X is a halogen. The stability of the halides decreases in the order F^– > Cl^– > Br^– > I^–. Amongst hexahalides, hexafluorides are the only stable halides. All hexafluorides are gaseous. They have an octahedral structure. Sulphur hexafluoride, SF₆ is exceptionally stable for steric reasons.

Applications and Importance

The members find a lot of applications that are applicable in daily life and in studies. Logically, oxygen is largely involved in respiratory and combustion, and it is very important in the generation of energy and metabolism. It is also applied in some treatments in medicine, in welding, and in the cleaning of pure water. Sulphur is applied in making sulphuric acid, fertilizers, and in the vulcanization of rubbers. Selenium applies itself in electronics and photocopiers as an antioxidant dietary supplement. Tellurium applies itself in semiconductors, while polonium, being very rare, applies to nuclear reactors and research. On an academic level alone, these are such elements that look more given the many different chemicalities they possess and in what ways they are likely to affect living things and the environment.

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Some Solved Examples

Example 1
Question: The correct order of catenation is:

1. C > Sn > Si ≈ Ge
2. C > Si > Ge ≈ Sn
3. Si > Sn > C > Ge
4. Ge > Sn > Si > C

Solution: The property of elements to form long chains or rings by self-linking of their atoms through covalent bonds is known as catenation. In the carbon family, catenation decreases down the group. Only carbon atoms form double or triple bonds involving p\(\pi\)-p\(\pi\) multiple bonds with themselves. The homo atomic bond energies are as follows:
- C-C = 83 kcal/mol
- Si-Si = 54 kcal mol
- Ge-Ge = 40 kcal mol
- Sn-Sn = 37 kcal mol

There is a significant difference between the bond energies of C-C and Si-Si, but the difference is negligible for Ge-Ge and Sn-Sn. Thus, the correct order is C > Si > Ge ≈ Sn. Hence, the answer is option (2).

Example 2

Question: Identify the wrong statement in the following:

1. Acid rain is mostly because of oxides of nitrogen and sulphur
2. Chlorofluorocarbons are responsible for ozone layer depletion
3. The greenhouse effect is responsible for global warming
4. The ozone layer does not permit infrared radiation from the sun to reach the earth

Solution: Infrared radiation is most important for heating the atmosphere and the surface of the earth. These rays have high wavelengths and low frequency and are not very harmful. Ozone does not hinder infrared radiation. Hence, the wrong statement is option (4).

Example 3
Question: Arrange the following in order of increasing boiling point:

1. $H_2O$ < $H_2S$ < $H_2Se$ < $H_2Te$
2. $H_2S$ < $H_2O$ < $H_2Se$ < $H_2Te$
3. $H_2S$ < $H_2Se$ < $H_2O $< $H_2Te$
4. $H_2S$ < $H_2Se$ < $H_2Te$ < $H_2O$

Solution: The boiling point increases with the increase of Van der Waals forces between the molecules, and the Van der Waals forces increase with the increase of the size of the molecule. The abnormally high boiling point of $H_2O$ can be explained by hydrogen bonding. Therefore, the correct order is $H_2S$ < $H_2Se$ < $H_2Te$ < $H_2O$. Hence, the answer is option (4).

Summary

Group 16 consists of a group of chalcogens involving oxygen, sulfur, selenium, tellurium, and polonium. The change from non-metallic to metallic moves down the group, though some have quite a range of chemical behaviours from the different oxidation states they can adopt. In all, applications of these elements will range from absolutely key biological functions down to important industrial processes and very sharp, cutting-edge scientific research. Their chemical characteristics explain their very significant functions in living systems and in built environments.