Group 16 Elements: Hydrides, Oxides, and Halides

Vocabulary flashcards covering the trends, properties, structure, and reactivity of Group 16 hydrides, oxides, and halides.

Oxygen Covalency

The bonding limit of oxygen, which is restricted to a maximum of four (and in practice rarely exceeds two) due to the absence of $d$ orbitals in its valence shell.

Group 16 Hydrides

Compounds formed by all Group 16 elements having the general formula $H_2E$ (where $E = O, S, Se, Te, Po$).

Acidic Character of Group 16 Hydrides

The acidic character trend $H_2O < H_2S < H_2Se < H_2Te$, which increases down the group due to the decrease in $H-E$ bond dissociation enthalpy.

Thermal Stability of Group 16 Hydrides

The stability trend that decreases from $H_2O$ to $H_2Po$ down the group owing to the decrease in bond dissociation enthalpy of the $H-E$ bond.

Reducing Property of Group 16 Hydrides

A property possessed by all Group 16 hydrides except water, increasing in strength from $H_2S$ to $H_2Te$.

Group 16 Hydride Dissociation Constants ($K_a$)

Aqueous dissociation constants at $298\,K$ that increase down the group: $1.8 \times 10^{-16}$ for $H_2O$, $1.3 \times 10^{-7}$ for $H_2S$, $1.3 \times 10^{-4}$ for $H_2Se$, and $2.3 \times 10^{-3}$ for $H_2Te$.

Group 16 Dioxides ($EO_2$)

Oxides formed by Group 16 elements where $O_3$ and $SO_2$ are gases, $SeO_2$ is a solid, and reducing property decreases from $SO_2$ (reducing) to $TeO_2$ (an oxidising agent).

Group 16 Trioxides ($EO_3$)

Acidic oxides formed by sulphur, selenium, and tellurium, represented by $SO_3$, $SeO_3$, and $TeO_3$.

Group 16 Halide Stability Order

The order of stability among halogens reacting with Group 16 elements, decreasing as $F > Cl > Br > I$.

Group 16 Hexafluorides

The only stable hexahalides of Group 16 elements, all of which are gaseous in nature with octahedral structures.

Sulphur Hexafluoride ($SF_6$)

An exceptionally stable gaseous hexahalide of Group 16 that owes its stability to steric reasons.

Group 16 Tetrafluorides

Fluorides including $SF_4$ (gas), $SeF_4$ (liquid), and $TeF_4$ (solid) possessing $sp^3d$ hybridisation.

See-saw Geometry

The trigonal bipyramidal geometry exhibited by Group 16 tetrafluorides in which one equatorial position is occupied by a lone pair of electrons.

Group 16 Dichlorides and Dibromides

Halides formed by $sp^3$ hybridisation with tetrahedral geometry, produced by all Group 16 elements except oxygen.

Group 16 Monohalides

Halides formed by Group 16 elements that are characteristically dimeric in nature.