Group 16 - The Chalcogens Lecture Review

Vocabulary flashcards covering the periodic trends, hydrides, halides, polyions, and sulfur-nitrogen compounds of Group 16 elements.

Group 16 Elements (Chalcogens)

A group of elements consisting of oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po), with properties ranging from non-metallic gases to metallic solids.

Valence Electron Configuration of Group 16

All elements in Group 16 have an $ns^2 np^4$ valence electron configuration.

Oxidation States of Group 16

The $-2$ oxidation state is common for all elements, while heavier elements can form hypervalent compounds reaching the group oxidation state of $+6$. Oxygen is limited to a maximum of $+2$ (in $OF_2$).

Group 16 Hydrides ($H_2E$) Bond Angle Trend

Bond angles decrease down the group: $H_2O$ ($104.5^ egular{ extdegree}$) > $H_2S$ ($92.1^ egular{ extdegree}$) > $H_2Se$ ($91^ egular{ extdegree}$) > $H_2Te$ ($90^ egular{ extdegree}$), indicating a transition from $sp^3$ hybridization to nearly pure p-orbitals in bonding.

$SF_6$ (Sulfur Hexafluoride)

A famously inert and non-toxic compound due to kinetic stability; the sulfur atom is sterically crowded, preventing nucleophilic attack.

$TeF_6$ (Tellurium Hexafluoride)

A reactive compound that hydrolyses easily because the larger tellurium atom is more accessible to nucleophiles compared to sulfur.

$TeCl_4$ (Tellurium Tetrachloride)

A stable tetrahalide of tellurium that exists as a tetramer in its solid state.

Polysulfides ($S_n^{2-}$)

Polyanions of sulfur organized in zigzag chains, such as those found in $Na_2S_4$.

Group 16 Polycations

Brightly colored polyatomic cations formed in strong oxidizing agents like oleum, including $S_4^{2+}$ (yellow), $S_8^{2+}$ (blue), and $Se_4^{2+}$ (yellow-orange).

$S_4N_4$ (Tetrasulfur Tetranitride)

An orange-red crystalline solid that is shock-sensitive and explosive, featuring a unique "cradle" structure with $S-S$ bonding interactions across the ring.

$(SN)_x$ (Poly(sulfur nitride))

A one-dimensional metallic conductor formed from the polymerization of $S_2N_2$ that becomes a superconductor at $0.26\,K$.

Hypervalency Bonding Models

Traditional Valence Bond models explain compounds like $SF_6$ using $sp^3d^2$ hybridization, whereas modern MO models for octahedral ($O_h$) symmetry explain bonding without relying heavily on high-energy d-orbitals.