The alkali metals

• Alkali metals are lithium, sodium, potassium, rubidium, caesium and francium.

• Each metal has a ground state valence electronic configuration ns 1.

• The heaviest member, francium, is usually neglected in discussions.

• Sodium and potassium are abundant in the Earth’s biosphere but do not occur naturally in the elemental state.

• The main sources of Na and K are rock salts, natural brines and seawater, sylvite, sylvinite and carnallite.

• NaCl don’t need to be manufactured since large natural deposits are available in seawater.

• Natural abundance of Li, Rb and Cs are small.

• These metals occur as various silicate minerals.

Sodium is economically the most important of the alkali metals. It is manufactured by the Downs process in which molten NaCl is electrolysed. CaCl2 is added to reduce the operating temperature to about 870 K, since pure NaCl melts at 1073 K.

Lithium is extracted from LiCl in a similar process like sodium. LiCl is first obtained from spodumene by heating with CaO to give LiOH, which is then converted to the chloride.

Potassium can be obtained electrolytically from KCl, but a more efficient method of extraction is the action of Na vapor on molten KCl in a counter-current fractionating tower.

Rb and Cs can be obtained from RbCl and CsCl, small quantities of which are produced as by-products from the extraction of Li from spodumene.

Small amounts of Na, K, Rb and Cs can be obtained by thermal decomposition of their azides.

Lithium has the lowest density of all known metals. It is used in the manufacture of alloys, and in certain glasses.

Lithium carbonate is used in treatment of bipolar disorders, although large amounts of lithium salts damage the central nervous system.

Sodium, potassium and their compounds have many uses. Sodium-potassium alloy is used as a heat-exchange coolant in nuclear reactors.

Both Na and K are involved in various electrophysiological functions in higher animals.

A balanced diet therefore includes both Na+ and K+ salts.

Potassium is also an essential plant nutrient, and K+ salts are widely used as fertilizers.

Uses of Li and Na in batteries is wellknown.

The KO2 is used in breathing masks.

Many organic synthesis involve Li, Na or their compounds.

Alkali metals and some of their compounds also have uses in catalysts.

The alkali metals have the high thermal and electrical conductivity, luster, ductility, and malleability that are characteristic of metals. Each alkali metal atom has a single electron in its outermost shell. This valence electron is much more weakly bound than those in inner shells. As a result, the alkali metals tend to form singly charged positive ions (cations) when they react with nonmetals.

When the salt of an alkali metal is treated with concentrated HCl and is heated strongly with a Bunsen burner, a characteristic flame color is observed (Li-crimson ; Na-yellow ; K-lilac ; Rb-red-violet ; Cs-blue) and this flame test is used in qualitative analysis to identify the M+ ion.

Li, Na, K and Rb - silvery-white cast ; while Cs - golden-yellow cast

All are soft, Li the least, and the trend is consistent with their melting points.

The particularly low melting point of Cs means that it may be a liquid at ambient temperature in some hot climates.

• They are all soft metals and typically can be cut with a knife. ​

• The softness of the metal increases within the group; caesium is the softest of the alkali metals.​

• Alkali metals are generally very reactive and oxidize in the air. ​

• The reactivity increases within the group, with lithium having the lowest reactivity and caesium the highest. ​

• Therefore, all alkali metals except lithium have to be stored in mineral oil. ​

• All alkali metals react violently with water with the formation of the metal hydroxide and hydrogen. ​

• Again, lithium is the least reactive alkali metal and reacts ‘only’ quickly with water, whereas potassium, rubidium and caesium are more reactive and react violently with water.

• In terms of their pharmaceutical applications, alkali metals are not directly useable mainly because of their reaction behavior in aqueous media. ​

• Alkali metal halides, some oxides, carbonates, citrates and other salts are of medicinal interest.​

• NaCl and KCl solutions are important as oral rehydration salts, and KCl can also be used to treat potassium depletion.

peroxides, superoxides, suboxides and ozonides

• lithium oxide, Li2O, sodium peroxide, Na2O2, and the superoxides KO2, RbO2 and CsO2.

• Alkali metal carbonates and bicarbonates have wide-ranging pharmaceutical applications. ​

• Lithium bicarbonate or citrate is used in the treatment of BD, whereas potassium bicarbonate or citrate is used in over-the-counter drugs as active pharmaceutical ingredients (APIs) against urinary-tract infections.

• Lithium salts are well known for their use in batteries, metal alloys and glass manufacture. ​

• Li also has a clinical application in the treatment of manic depression or BD. ​

• BD affects 1–2% of the population and severely reduces the quality of life for the patients and also increases the likelihood of patients committing suicide.​

• Research has shown that lithium salts are very successful in the treatment of BD, and a broad research in this area has been stimulated.

1859 - the first medical use of lithium ; the treatment of rheumatic conditions and gout.

1880 - first reported as being used in the treatment of BD ; LiCl was prescribed as a replacement for NaCl in diet

1929 - soft drink 7Up marketed, containing LiCl and lithium citrate, as a hangover cure

1949 - discovery of lithium as a sedative and mood-controlling medicine

1970 - lithium is used in 50% of treatment for BD

The size of an atom decreases within the same period (from left to right). The reason is that a positive charge is added to the nucleus together with an extra electron orbital.

Trends can be seen for the electronegativity and the ionization energy; both increase when moving within the same period from left to right and decrease within the same group.

structure of trends is summarized under this term

• Lithium has a very narrow therapeutic window, which makes the monitoring of blood levels essential during the treatment. ​

• More than 1.5 mmol/l Li+ in the blood plasma may cause toxic effects, usually tremors in the fingers, renal impairment and convulsion. ​

• Also, memory problems are a very common side effect.

• Extreme doses of lithium can cause nausea and diarrhea, and doses above 2 mmol/l require emergency treatment, as these levels may be fatal. ​

• Weight gain and decreased thyroid levels are also commonly reported problems.

• Lithium salts have severe adverse effects on the renal system. ​

• Lithium therapy can damage the internal structures of the kidneys.

• an essential ion of the human body

• Sodium has atomic number 11 and has the symbol Na, derived from the Latin name ‘natrium’. ​

• Sodium ions (Na+) are soluble in water and therefore present in large quantities in the oceans. ​

• Na+ is also part of minerals and an essential element for all animal life.

• The main biological roles of sodium ions are the maintenance of body fluids in humans and the functioning of neurons and transmission of nerve impulses. ​

• Na+ is an important electrolyte and a vital component of the extracellular fluid. ​

• Na+ ions also play a crucial role in the contraction of muscles and in the mode of action of several enzymes.

is defined as the physical process of diffusion of a solvent (water) through a semi-permeable membrane towards an area of high solute (salt) concentration.

is a medium that has a higher concentration of solutes than the surrounding area. This area will lose water through osmosis.

is a medium that has a lower concentration of solutes that the surrounding area. This area will gain water through osmosis.

is a medium that has the same concentration of solutes as the surrounding area. No movement of water will occur.

is defined as the pressure that is required to establish equilibrium with no movement of solvents. It depends on the number of ions or molecules in the solution, not the identity of those.

is the resulting electrostatic potential that is built up along the cell membrane and is responsible for the transmission of nerve impulses.

• Potassium has atomic number 19 and the chemical symbol K, which is derived from its Latin name ‘kalium’.​

• Potassium was first isolated from potash, which is potassium carbonate (K2CO3). ​

• Potassium occurs in nature only in the form of its ion (K+) either dissolved in the ocean or coordinated in minerals because elemental potassium reacts violently with water. ​

• Potassium ions are essential for the human body and are also present in plants.

• The major use of K+ can be found in fertilizers, which contains a variety of potassium salts such as potassium chloride (KCl), potassium sulfate (K2SO4) and potassium nitrate (KNO3).​

• KCl is also found in table salt, whereas potassium bromate (KBrO3) is an oxidizing agent and is used as flour improver. ​

• Potassium bisulfite (KHSO3) can be used as a food preservative in wine and beer.

By exceeding the daily amount recommended of salt intake, you can develop hypernatremia which is high salt plasma levels that can result in cardiovascular disorders such as hypertension.

is a disease where you have low salt plasma levels which can be a result in dysfunction of kidneys or sodium loss in the bowels, also cause damage to the human body via osmotic imbalance.

is a potentially serious condition where the patient has low levels of K+ in his/her blood plasma.  Symptoms can include weakness of the muscles or ECG (electrocardiogram) abnormalities.

Hypokalemia is often found in patients treated with diuretics such as loop diuretics and thiazides.

• Although Li, Na and K are stored under a hydrocarbon solvent to prevent reaction with atmospheric O2 and water vapor, they can be handled in air, provided undue exposure is avoided. ​

• Rb and Cs should be handled in an inert atmosphere.​

• Lithium reacts quickly with water; Na reacts vigorously, and K, Rb and Cs react violently with the ignition of H2 produced.