Lithium is a soft, silvery-white metal and the lightest solid element in the periodic table. It belongs to Group 1, also known as the alkali metals, and has an atomic number of 3. It was discovered in 1817 and is mainly obtained from minerals like spodumene and lepidolite. Lithium is widely used in rechargeable batteries, medicines, and lightweight metal alloys. It is highly reactive and flammable, especially in moist air and water. Due to its unique properties, lithium plays an important role in modern technology and industry.
Causes of Peculiar Behavior
The first member of every main group of the periodic table is unique. In many of its properties, Lithium is entirely different from other members of group IA. The deviation shown by lithium from the regular trend of the group is due to the following reasons:
- The atomic radius of Lithium is very small as compared to the other members of group I.
- Li+ ion has a greater charge density.
- The nuclear charge of the Li+ ion is screened only by a shell of two electrons.
The so-called’ anomalous’ properties of Lithium are because Lithium is unexpectedly far less electropositive than sodium.
Difference of Lithium from Other Alkaline Earth Metals
1. Lithium is much harder and lighter than the alkali metals.
2. The Lithium salts of anions with high density are generally less soluble in water than those of the other alkali metals. e.g., LiOH, LiF, Li₃PO₄, Li₂CO₃.
3. Lithium forms stable complex compounds, although complex formation generally is not a property of alkali metals. One of the stable complexes formed by Lithium [⁺
4. Lithium reacts very slowly with water, while other alkali metals react violently.
2Li + 2H₂O → 2LiOH + H₂↑
5. Lithium salts of large polarizable anions are less stable than those of the other alkali metals. Unlike other alkali metals, Lithium does not form bicarbonate, triiodide, or hydrogen sulfide at room temperature.
6. When burnt in air, Lithium forms only normal oxide, whereas the others form peroxides or superoxides.
2Na + O₂ → Na₂O₂ ( Sodium Peroxide)
4Li + O₂ → 2Li₂O ( Lithium oxide)
7. Lithium hydride is more stable than the hydrides of other alkali metals.
8. Lithium compounds are more covalent, which is why their halides are more soluble in organic solvents and the alkyls and aryls of Lithium are more stable than those of all the alkali metals.
9. Lithium is the least reactive metal of all the alkali metals.
10. When acetylene is passed over strongly heated Lithium, it does not produce Lithium acetylide, but other alkali metals form the corresponding metallic acetylides.
C₂H₂ + 2Na → Na⁺C≡C⁻Na⁺ + H₂ ( Sodium Acetylide)
11. Lithium has a low electropositive character; thus, its carbonate and nitrate are not so stable and therefore decompose, giving lithium oxide. Carbonates of other alkali metals do not decompose. Decomposition of Lithium nitrate gives different products than the nitrates of other alkali metals.
Li₂CO₃ → Li₂O + CO₂↑
4LiNO₃ → 2Li₂O + 4NO₂ + O₂
2NaNO₃ → 2NaNO₂ + O₂
12. Lithium hydroxide, when strongly heated, forms Lithium oxide, but the other alkali metals’ hydroxides do not show this behavior.
2LiOH → Li₂O + H₂O
13. Lithium reacts with nitrogen to form nitrides, while the other members of the group do not react.
6Li + N₂ → 2Li₃N
14. Lithium Chloride has an exothermic heat of solution, whereas the chlorides of sodium and potassium have endothermic heats of solution.
15. Lithium carbide is the only alkali metal carbide formed readily by direct reaction.
4Li + C → Li₂C₂
Conclusion
In conclusion, lithium’s unusual behavior sets it apart within the alkali metal family.
Its unique properties are due to its small atomic size and high polarizing power.
These differences impact its bonding, solubility, and the nature of its compounds.
Lithium’s exceptional chemistry proves that even in a group, individuality stands strong.
