The basic inorganic salt chemistry of lithium is fundamentally similar to that of sodium and potassium. However, there are some significant differences that make lithium unique.
In the alkali metals family, lithium tends to go against the typical behavior and this is due to it's unique nucleus.
Lithium atoms have three protons, three or four neutrons, and three electrons. Sodium atoms have 11 protons, 12 neutrons and 11 electrons. Potassium atoms have 19 protons, 20 neutrons, and 19 electrons.
In each of these atoms the protons and neutrons are in the nucleus and the electrons are in orbital clouds that surround the nucleus.
When we consider solution chemistry of these metal ions, it's important that we don't think about them as little positively charged balls because a lot more is happening rather than simple positive-negative interactions.
Alkali Metal Ions
In alkali metal ions, the nucleus itself plays a big part in how its ion behaves.
Furthermore, nuclear influence is affected by how well it is shielded by the electrons that surround it.
For example, potassium has 19 protons, so in its ionic state, it has 18 electrons. Therefore, 95% of the proton charge is “shielded” by the electrons in the ion.
Lithium ions have two electrons and three protons. Only 66% of its protons are balanced by the electrons in the ion. Therefore, the lithium nucleus is poorly shielded.
Because of this, neutral oxygen-containing molecules are strongly attracted to lithium ions, explaining lithium’s odd solubility behavior.
Li+ tends to hold more water around it than other alkali metal ions.
The field of organometallic chemistry is one in which Lithium's unique structure and chemistry come into play. Organolithium compounds such as butyllithium, C4 H9 Li, are highly reactive.
Organolithium reagents can be used to add chemical groups to very specific locations on highly complex molecules such as drug precursors.
Many of these chemicals are highly susceptible to temperature changes, so one of the key benefits of organolithium compounds is that they are highly reactive in extremely cold conditions.
They can also be designed to conduct very specific reactions, with essentially no side reactions.
Lithium's High Reaction Efficiency
The combination of extreme specificity and high reactivity can lead to very high reaction efficiencies. Organolithium compounds have been used to manufacture different medicines, such as statins.
Organolithium compounds are also utilized as certain polymer initiators. They can initiate polymer reactions and continue to build the polymer by adding other molecules to the chain, so they basically form a “living end” that can be extended.
This technology is used in numerous products, including high mileage and smooth riding rubber for tires.