CHEM2077: Group 1 - The Alkali Metals

Flashcards covering physical properties, ionization enthalpy, reduction potentials, halide structures, and specialty topics like Li-ion batteries and organometallics for Group 1 elements.

Group 1 Members

The alkali metals consisting of Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), and Francium (Fr).

Atomic Radii Trend

Increases significantly down the group: Li ($152\,pm$) < Na ($186\,pm$) < K ($231\,pm$) < Rb ($244\,pm$) < Cs ($262\,pm$).

Valence Electron Configuration

The general outer shell electron arrangement for alkali metals, denoted as $ns^1$.

First Ionization Energy

Commonly low for Group 1 metals and decreases down the group as the valence electron becomes further from the nucleus.

Second Ionization Energy

Extremely high for Group 1 metals as it requires removing an electron from a stable, closed-shell noble gas configuration.

Reduction Potential ($E^\circ$)

Measured in Volts; a large negative value indicates the metal is a strong reducing agent that is easily oxidized.

Gibbs Free Energy Equation

The thermodynamic relationship defined as $\Delta G^\circ = -nFE^\circ$.

Lithium Anomaly

Lithium has a more negative reduction potential ($-3.05\,V$) than predicted by ionization enthalpy alone due to the high hydration enthalpy of the small, charge-dense $Li^+$ ion.

Hydration Enthalpy ($M^+(g) \rightarrow M^+(aq)$)

The biggest variable in reduction potentials across Group 1.

NaCl (Rock Salt) Structure

An ionic lattice featuring 6:6 octahedral coordination.

CsCl Structure

An ionic lattice featuring 8:8 cubic coordination, also adopted by CsBr and CsI.

Radius Ratio

The ratio of the cation radius to the anion radius, which primarily determines the lattice structures of halides.

$\Delta_fH^\circ$ Trend (Fluorides)

Enthalpy of formation becomes less negative down the group because the decrease in lattice energy dominates.

$\Delta_fH^\circ$ Trend (Cl, Br, I)

Enthalpy of formation becomes more negative down the group because internal variations in sublimation and ionization energies dominate over lattice energy variations.

LiF (Lithium Fluoride)

The only Group 1 halide that is water-insoluble due to an extremely high lattice enthalpy that is not offset by hydration enthalpy.

Lithium-Ion Battery Metallic Content

Contrary to belief, these batteries contain zero metallic lithium, containing only $Li^+$ ions.

Lithium-Ion Battery Anode

Consists of lithium ions between layers of reduced graphite, represented as $Li_xC$.

Lithium-Ion Battery Cathode

Consists of lithium ions in an oxidized cobalt oxide, represented as $Li_yCoO_2$.

Methyllithium ($MeLi$)

An organometallic species with significant covalent character that exists as a tetramer $(MeLi)_4$.

4-center 2-electron bonds

The specific type of bonding found in the tetrameric structure of methyllithium.