Name: Allotropes of Sulphur
Uploaded: 2019-07-19
Duration: 6 min 39 s
Description: Sulphur is one of the most useful non-metals which has wide applications in our industries. Watch this video to learn about the important allotropes of sulphur.

Question

Give a comparative account of Group 16 elements (Oxygen family) of periodic table.

Accepted Answer

Trends in physical properties of Group 16 elements :

Electronic configuration :

The general outermost electronic configuration of Group 16 elements is given by ${ns}^{2} {np}^{4}$ .

Atomic radii :

Atomic radius or size increases from oxygen to polonium. This is due to the addition of electronic shells with increase in atomic numbers.

Ionisation enthalpy :

Ionisation enthalpy decreases down the group due to increase in size. The elements of this group possess lower ionisation enthalpy values as compared to the Group 15 elements of the same period because of their extra ability due to half filled $p -$ orbitals.

Electronegativity :

Oxygen is the most electronegative element in the group. Next to fluorine it has the highest electronegative value among the elements. The electronegativity decreases down the group and hence metallic character increases from oxygen to polonium.

Physical state :

Oxygen exists as a diatomic gas at room temperature. Sulphur, selenium, tellurium exists as octane atomic solids and polonium is a radioactive metal with a very short half-life.

Chemical properties of group 16 elements :

Oxidation states :

The elements of Group 16 exhibits a number of oxidation states. The stability of $- 2$ oxidation state decreases down the group. Polonium hardly shows $- 2$ oxidation state. Since, electronegativity of oxygen is very high, it shows only negative oxidation state as $- 2$ except in the case of ${OF}_{2}$ 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 $+ 4$ oxidation state in their compounds with oxygen and $+ 6$ with fluorine. The stability of $+ 6$ oxidation state decreases down the group and stability of $+ 4$ oxidation state increases. Bonding in $+ 4$ and $+ 6$ oxidation states is primarily covalent.

(i) Reactivity with hydrogen: All the elements of Group 16 formhydrides of the type $H_{2} E (E = O, S, Se, Te, Po)$ . The acidic character of hydrides increases from $H_{2} O$ to $H_{2} Te$ . 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 $H - E$ bond down the group, the thermal stability of hydrides also decreases from $H_{2} O$ to $H_{2} Po$ . All the hydrides except water possess reducing property and this character increases from $H_{2} S$ to $H_{2} Te$ .

(ii) Reactivity with oxygen: All these elements form oxides of the ${EO}_{3}$ and ${EO}_{2}$ types where $E = S, Se, Te, Po$ . Ozone and sulphur dioxide are gases while selenium dioxide is solid.

Reducing property of dioxide decreases from ${SO}_{2}$ to ${TeO}_{2}$ ; ${SO}_{2}$ is reducing while ${TeO}_{2}$ is an oxidising agent. Besides ${EO}_{2}$ type,sulphur, selenium and tellurium also form ${EO}_{3}$ type oxides ( ${SO}_{3}, {SeO}_{3}, {TeO}_{3}$ ). Both types of oxides are acidic in nature.

(iii) Reactivity towards the halogens: Elements of Group 16 form large number of halides of the type ${EX}_{6}, {EX}_{4}$ and ${EX}_{2}$ 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 in nature. They have octahedral structure. Sulphur hexafluoride, is exceptionally stable for steric reasons.

Give a comparative account of Group 16 elements (Oxygen family) of periodic table.

Important Questions on Group 16 Elements : Oxygen Family

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