Discuss the chemical properties of Group $16$ elements.

(N/A) $(i)$ Reactivity with hydrogen: All Group $16$ elements form hydrides of the type $H_2E$ (where $E = O, S, Se, Te, Po$).
Their acidic character increases from $H_2O$ to $H_2Te$. This increase in acidic character is due to the decrease in bond dissociation enthalpy of the $H-E$ bond down the group.
Thermal stability of hydrides decreases from $H_2O$ to $H_2Po$ due to the decrease in $H-E$ bond dissociation enthalpy down the group.
All hydrides except water possess reducing property,and this character increases from $H_2S$ to $H_2Te$.
$(ii)$ Reactivity with oxygen: All these elements form oxides of the types $EO_2$ and $EO_3$ (where $E = S, Se, Te, Po$).
Ozone $(O_3)$ and sulfur dioxide $(SO_2)$ are gases,while selenium dioxide $(SeO_2)$ is a solid. The reducing property of dioxides decreases from $SO_2$ to $TeO_2$; $SO_2$ is a reducing agent,while $TeO_2$ is an oxidizing agent. Sulfur,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 with halogens: Group $16$ elements form a large number of halides of the types $EX_6, EX_4,$ and $EX_2$ (where $E$ is an element of this group and $X$ is a halogen).
The stability of halides decreases in the order: $F^- > Cl^- > Br^- > I^-$.
Among hexahalides,only hexafluorides are stable. All hexafluorides are gaseous and have octahedral geometry.
Sulfur hexafluoride,$SF_6$,is exceptionally stable for steric reasons.
Among tetrafluorides,$SF_4$ is a gas,$SeF_4$ is a liquid,and $TeF_4$ is a solid. These fluorides have $sp^3d$ hybridization and thus possess a trigonal bipyramidal geometry,in which one equatorial position is occupied by a lone pair of electrons. This geometry is also called the see-saw geometry.
All elements except oxygen form dichlorides and dibromides. These dihalides are formed by $sp^3$ hybridization and thus have a tetrahedral structure.
Well-known monohalides are dimeric in nature. Examples include $S_2F_2, S_2Cl_2, S_2Br_2, Se_2Cl_2,$ and $Se_2Br_2$. These dimeric halides undergo disproportionation reactions,e.g.,$2Se_2Cl_2 \rightarrow SeCl_4 + 3Se$.