Anomalous Behaviour of Lithium: Explanation and Properties

Anomalous Behaviour of Lithium

Edited By Shivani Poonia | Updated on Jul 02, 2025 05:56 PM IST

Lithium, the third element in the periodic table and the lightest metal is unique among alkali metals in a lot of remarkable ways. The high reactivity and electrochemical potential of lithium are well recognized. In some physical and chemical properties, lithium is significantly different from its heavier equivalents in Group 1 because of its small atomic and ionic size, high charge density, and distinct electronic configuration. Among the many amazing anomalous behaviors that lithium displays is its diagonal interaction with the Group 2 element magnesium.

Anomalous Behaviour of Lithium

Features that are similar to those of other alkali metals but are not typically observed, such as covalent character in compounds and covalent character in compounds. Moreover, lithium has higher melting, boiling, and hardness points than potassium and sodium, which are its group neighbors. These differences highlight how crucial it is to understand lithium's unusual behavior to fully realize its promise for a variety of technical improvements, including the development of improved ceramics, lightweight alloys, and rechargeable batteries.

Anomalous Behaviour of Lithium:

The anomalous behavior of lithium is due to the

1. Exceptionally small size of its atom and ion

2. High polarising power.

As a result, there is increased covalent character of lithium compounds which is responsible for their solubility in organic solvents. Further, lithium shows a diagonal relationship to magnesium which has been discussed subsequently.

Points of Difference between Lithium and other Alkali Metals

Lithium is much harder. Its m.p. and b.p. are higher than the other alkali metals.
Lithium is the least reactive but the strongest reducing agent among all the alkali metals. On combustion in air, it forms mainly monoxide, Li₂O, and nitride, Li₃N, unlike other alkali metals.
LiCl is deliquescent and crystallizes as a hydrate, LiCl.2H₂O whereas other alkali metal chlorides do not form hydrates.
Lithium hydrogen carbonate is not obtained in the solid form while all other elements form solid hydrogen carbonates.
Lithium unlike other alkali metals forms no ethynide in reaction with ethyne.
Lithium nitrate when heated gives lithium oxide, Li₂O, whereas other alkali metal nitrates decompose to give the corresponding nitrite.
LiF and Li₂O are comparatively much less soluble in water than the corresponding compounds of other alkali metals.

Points of Similarities between Lithium and Magnesium

Both lithium and magnesium are harder and lighter than other elements in the respective groups.
Lithium and magnesium react slowly with water. Their oxides and hydroxides are much less soluble and their hydroxides decompose on heating.
The oxides, Li₂O and MgO do not combine with excess oxygen to give any superoxide.
The carbonates of lithium and magnesium decompose easily on heating to form oxides and CO₂.
Both LiCl and MgCl₂ are soluble in ethanol.
Both LiCl and MgCl₂ are deliquescent and crystallize from aqueous solution as hydrates.

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Some Solved Examples

Q.1 Which of the following compounds is formed when Li is exposed to air?

1)Li₄N⁺

2)Li₂N

3)Li₃N

4)All of these

Solution:

As we learned,

Action of air on Lithium (anomaly)

Lithium reacts with N₂ as well other alkali metals do not react with N₂

$6 \mathrm{Li}(\mathrm{s})+\mathrm{N}_2(g) \rightarrow 2 \mathrm{Li}_3 N(s)$

Li reacts with N₂present in the air and forms its nitride, Li₃N

Hence, the answer is the option (3).

Q.2 Which of the following is the strongest reducing in nature?

1) Li

2) K

3) Na

4) Rb

Solution:

As we learned,

The greater reducing power of lithium is due to its large heat of hydration which is due to its smaller size and high charge density.

Hence, the answer is the option (1).

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Conclusion

Among the alkali metals, lithium, the third element and lightest metal in the periodic table, stands out for its unusual chemical as well as physical properties. Its high charge density, distinct electronic configuration, and small atomic and ionic size all contribute to its unusual behavior when compared to its Group 1 counterpart. These variations show up as greater melting, boiling, and hardness points, as well as a diagonal relationship with magnesium and the capacity to create covalent compounds.

Due to its high reactivity and electrochemical potential, lithium is a great material for energy storage systems, especially when it comes to the creation of lithium-ion batteries. Its special qualities also hold great potential for improvements in chemistry and materials research, including the development of lighter alloys and improved ceramics. To fully utilize lithium in a variety of technological disciplines, one needs to understand the peculiar behavior of this material. Our ability to investigate and utilize these unique qualities will help us to propel innovations that result in more productive and successful uses in materials engineering, energy storage, and other fields.

Frequently Asked Questions (FAQs)

1. What makes lithium exceptional among the alkali metals?

As lithium's properties are so distinct from those of the remaining alkali metals in Group 1 of the periodic table, it is considered as anomalous.

2. What is the reactivity of lithium with respect to other alkali metals?

Unlike other alkali metals like potassium and sodium, lithium is less reactive.

3. How do lithium's colours appear in flame tests?

Lithium gives a crimson-red colour to the flames.

4. Why does lithium, in contrast to other alkali metals, produce a stable nitride?

Lithium forms strong ionic interactions with nitrogen, therefore it produces a stable nitride (Li₃N).

5. What makes lithium an essential component of rechargeable batteries?

Due to its high electrochemical potential, lightweight nature, and versatility.

6. Why does lithium have a higher lattice energy in its compounds compared to other alkali metals?

Lithium compounds have higher lattice energies due to lithium's small size and high charge density. The strong electrostatic attraction between the small Li+ ion and anions results in more tightly packed crystal structures with higher lattice energies compared to compounds of other alkali metals.

7. Why does lithium have a lower coefficient of thermal expansion compared to other alkali metals?

Lithium has a lower coefficient of thermal expansion due to its stronger interatomic forces. The small size and high charge density of lithium atoms result

8. Why does lithium form more covalent compounds than other alkali metals?

Lithium forms more covalent compounds because of its small size and high charge density. This allows lithium to polarize larger anions more effectively, leading to shared electron pairs rather than complete electron transfer, resulting in more covalent character in its compounds.

9. Why is lithium considered "anomalous" among the alkali metals?

Lithium is considered anomalous because it exhibits several properties that differ significantly from the general trends observed in other alkali metals. These differences arise due to its small size, high charge density, and strong polarizing power, which lead to unique chemical and physical behaviors compared to its larger counterparts in Group 1.

10. How does the atomic size of lithium compare to other alkali metals?

Lithium has the smallest atomic size among alkali metals. This is because it has the fewest electron shells and the strongest effective nuclear charge, pulling its electrons closer to the nucleus compared to other elements in Group 1.

11. Why does lithium have a higher melting and boiling point than other alkali metals?

Lithium has higher melting and boiling points due to its smaller size and stronger metallic bonding. The electrons in lithium are held more tightly, requiring more energy to break the bonds between atoms, resulting in higher melting and boiling points compared to other alkali metals.

12. How does lithium's reactivity with water compare to other alkali metals?

Lithium is less reactive with water compared to other alkali metals. While it does react, the reaction is slower and less vigorous. This is due to its higher ionization energy and the formation of a protective lithium hydroxide layer on its surface, which slows down further reaction.

13. Why does lithium form a stable carbonate while other alkali metal carbonates decompose easily?

Lithium carbonate (Li2CO3) is more stable because of the high lattice energy resulting from lithium's small size and high charge density. This strong ionic bonding makes it resistant to thermal decomposition, unlike the carbonates of larger alkali metals.

14. How does lithium's flame color differ from other alkali metals, and why?

Lithium produces a distinctive red flame color, while other alkali metals produce different colors (e.g., sodium - yellow, potassium - lilac). This is due to the unique energy levels of lithium's electrons, which emit red light when excited and returning to their ground state.

15. How does lithium's ability to form alloys differ from other alkali metals?

Lithium has a greater tendency to form alloys with other metals compared to other alkali metals. Its small size allows it to fit into interstitial spaces in metal lattices more easily, forming stable alloys with a wide range of metals, including those that don't typically alloy with other alkali metals.

16. Why does lithium have a higher electrical resistivity than other alkali metals?

Lithium has a higher electrical resistivity because its electrons are more tightly bound to the nucleus. This stronger electron-nucleus interaction makes it more difficult for electrons to move freely through the metal, resulting in higher resistance to electrical current flow compared to other alkali metals.

17. How does lithium's crystal structure differ from other alkali metals at room temperature?

At room temperature, lithium adopts a body-centered cubic (BCC) crystal structure, while other alkali metals have a face-centered cubic (FCC) structure. This difference is due to lithium's smaller size and stronger metallic bonding, which favor the more compact BCC arrangement.

18. How does lithium's ability to intercalate into other materials differ from other alkali metals?

Lithium has a superior ability to intercalate (insert itself) into layered materials due to its small size. This property is crucial in lithium-ion batteries, where lithium ions can easily move in and out of electrode materials, a capability not shared to the same extent by other alkali metals.

19. How does lithium's ability to form clusters in the gas phase compare to other alkali metals?

Lithium has a greater tendency to form clusters in the gas phase compared to other alkali metals. Its small size and high charge density allow for stronger interactions between lithium atoms, leading to the formation of stable clusters (e.g., Li2, Li4) more readily than other alkali metals.

20. How does lithium's behavior in liquid ammonia differ from other alkali metals?

In liquid ammonia, lithium behaves differently from other alkali metals. While all alkali metals dissolve to form blue solutions, lithium's solution is less intensely colored and more stable. This is due to its higher ionization energy and stronger interaction with ammonia molecules.

21. How does lithium's behavior in the solid state differ from other alkali metals at low temperatures?

At low temperatures, lithium retains its body-centered cubic (BCC) structure, while other alkali metals undergo phase transitions to different crystal structures. This stability is due to lithium's stronger metallic bonding and smaller size, which maintain the BCC arrangement even at low temperatures.

22. Why does lithium form more stable complexes with crown ethers compared to other alkali metals?

Lithium forms more stable complexes with crown ethers because its small size allows it to fit perfectly into the cavity of smaller crown ethers. This results in stronger binding and more stable complexes compared to larger alkali metals, which require larger crown ethers for optimal binding.

23. How does lithium's ability to form solid electrolyte interphase (SEI) layers in batteries differ from other alkali metals?

Lithium forms more stable and effective solid electrolyte interphase (SEI) layers in batteries compared to other alkali metals. Its small size and high reactivity allow for the formation of a protective layer on electrode surfaces, crucial for the long-term stability and performance of lithium-ion batteries.

24. Why does lithium have a higher thermal conductivity compared to other alkali metals?

Lithium has a higher thermal conductivity due to its lighter mass and stronger interatomic forces. These properties allow for more efficient transfer of thermal energy through the metal lattice, resulting in better heat conduction compared to heavier alkali metals.

25. How does lithium's behavior in high-pressure environments differ from other alkali metals?

Under high pressure, lithium exhibits unique behavior compared to other alkali metals. It can transform into unexpected structures, including one that behaves like a semiconductor. This is due to its small size and the ability of its electrons to rearrange under extreme conditions.

26. How does lithium's ability to form intermetallic compounds differ from other alkali metals?

Lithium has a greater tendency to form intermetallic compounds compared to other alkali metals. Its small size allows it to fit into interstitial spaces or form new crystal structures with a wide range of metals, resulting in a diverse array of intermetallic compounds with unique properties.

27. How does lithium's behavior in non-polar solvents differ from other alkali metals?

In non-polar solvents, lithium shows greater solubility and stability compared to other alkali metals. Its small size and high charge density allow for better interaction with non-polar molecules, often forming solvated electron solutions more readily than its larger counterparts.

28. How does lithium's ability to form glasses differ from other alkali metals?

Lithium has a greater ability to form glasses compared to other alkali metals. Its small size allows it to fit into glass networks more easily, disrupting the structure less than larger alkali ions. This property makes lithium useful in creating specialized glasses with unique properties.

29. Why does lithium have a higher diffusion coefficient in solids compared to other alkali metals?

Lithium has a higher diffusion coefficient in solids due to its small size. The lithium ion can move more easily through crystal lattices and interstitial spaces, allowing for faster diffusion in various materials. This property is crucial for its use in solid-state batteries and other applications.

30. How does lithium's behavior in plasma states differ from other alkali metals?

In plasma states, lithium behaves differently from other alkali metals due to its higher ionization energy and smaller size. It requires more energy to fully ionize and can maintain partially ionized states under conditions where larger alkali metals would be fully ionized, affecting its spectroscopic and other plasma-related properties.

31. How does lithium's hydration energy compare to other alkali metals?

Lithium has the highest hydration energy among alkali metals. Its small size allows it to attract water molecules more strongly, forming a larger and more stable hydration shell compared to other alkali metals.

32. Why does lithium form a nitride (Li3N) while other alkali metals don't?

Lithium forms a nitride because its small size allows it to polarize the nitrogen molecule effectively. The high charge density of lithium enables it to break the strong triple bond in N2, forming Li3N. Larger alkali metals lack this ability due to their lower charge density.

33. How does lithium's first ionization energy compare to other alkali metals?

Lithium has the highest first ionization energy among alkali metals. This is due to its small atomic size and strong effective nuclear charge, which hold the outermost electron more tightly, requiring more energy to remove it compared to other alkali metals.

34. How does lithium's ability to form complexes compare to other alkali metals?

Lithium has a greater tendency to form complexes compared to other alkali metals. Its small size and high charge density allow it to interact more effectively with ligands, forming stable coordination compounds, especially with oxygen and nitrogen-containing ligands.

35. Why does lithium have a higher electronegativity than other alkali metals?

Lithium has a higher electronegativity due to its smaller atomic size and stronger effective nuclear charge. The valence electron is held more tightly to the nucleus, making lithium more likely to attract electrons in chemical bonds compared to other alkali metals.

36. Why does lithium form a stable oxide (Li2O) while other alkali metals form peroxides or superoxides?

Lithium forms a stable oxide (Li2O) because its small size and high charge density allow for strong ionic bonding with oxygen. Larger alkali metals, with lower charge densities, cannot stabilize the O2- ion as effectively, leading to the formation of peroxides (O22-) or superoxides (O2-).

37. How does lithium's solubility in organic solvents compare to other alkali metals?

Lithium is more soluble in organic solvents than other alkali metals. Its small size and high charge density allow it to interact more effectively with organic molecules, making it more soluble in solvents like ethers and hydrocarbons.

38. Why does lithium have a higher specific heat capacity compared to other alkali metals?

Lithium has a higher specific heat capacity due to its low atomic mass and strong interatomic forces. More energy is required to increase the temperature of a given mass of lithium compared to other alkali metals, resulting in a higher specific heat capacity.

39. Why does lithium have a lower electron affinity compared to other alkali metals?

Lithium has a lower electron affinity because its small size leads to greater electron-electron repulsion when an additional electron is added. The compact nature of the lithium atom makes it less favorable to accept an extra electron compared to larger alkali metals.

40. How does lithium's ability to form hydrogen bonds affect its properties?

Lithium's small size and high charge density allow it to form hydrogen bonds, particularly in its hydrated form. This ability to participate in hydrogen bonding affects its solubility, hydration energy, and interactions with biological molecules, setting it apart from other alkali metals.

41. Why does lithium have a higher tensile strength compared to other alkali metals?

Lithium has a higher tensile strength due to its stronger metallic bonding. The small size and high charge density of lithium ions result in stronger interactions between the metal atoms, making it more resistant to deformation under stress compared to other alkali metals.

42. Why does lithium form more stable organometallic compounds than other alkali metals?

Lithium forms more stable organometallic compounds because of its higher electronegativity and smaller size. These properties allow for stronger and more covalent carbon-lithium bonds, resulting in organolithium compounds that are more stable and useful in organic synthesis compared to other alkali metal organometallics.

43. How does lithium's behavior in non-aqueous solvents differ from other alkali metals?

In non-aqueous solvents, lithium exhibits greater stability and solubility compared to other alkali metals. Its small size and high charge density allow for better solvation and less reactivity, making it more suitable for applications in organic synthesis and battery technologies in non-aqueous environments.

44. Why does lithium have a lower first electron affinity than sodium, despite being smaller?

Lithium has a lower first electron affinity than sodium because its small size leads to greater electron-electron repulsion when an additional electron is added. The compact nature of the lithium atom makes it less energetically favorable to accept an extra electron compared to the larger sodium atom.

45. Why does lithium have a higher charge-to-radius ratio compared to other alkali metals?

Lithium has a higher charge-to-radius ratio because it has the smallest atomic radius among alkali metals while still carrying a +1 charge. This results in a more concentrated positive charge, leading to stronger electrostatic interactions and influencing many of its anomalous properties.

46. How does lithium's ability to form ionic liquids compare to other alkali metals?

Lithium is more effective at forming ionic liquids compared to other alkali metals. Its small size and high charge density allow for stronger interactions with large organic anions, resulting in ionic liquids with lower melting points and unique properties useful in various applications.

47. Why does lithium have a higher polarizing power than other alkali metals?

Lithium has a higher polarizing power due to its small size and high charge density. This allows lithium to distort the electron clouds of nearby ions or molecules more effectively, leading to more covalent character in its compounds and influencing its chemical behavior.

48. Why does lithium have a higher surface tension than other liquid alkali metals?

Lithium has a higher surface tension in its liquid state due to stronger cohesive forces between lithium atoms. The small size and high charge density of lithium result in stronger metallic bonding, leading to a higher surface tension compared to other liquid alkali metals.

49. How does lithium's ability to form solid solutions with other metals compare to other alkali metals?

Lithium has a greater ability to form solid solutions with other metals compared to other alkali metals. Its small size allows it to occupy interstitial sites in various metal lattices more easily, forming stable solid solutions with a wider range of metals.

50. Why does lithium have a lower vapor pressure compared to what would be expected based on trends in the alkali metal group?

Lithium has a lower vapor pressure than expected because of its stronger metallic bonding. The small size and high charge density of lithium atoms result in stronger cohesive forces within the metal, making it more difficult for atoms to escape into the gas phase.

51. How does lithium's behavior in molten salts differ from other alkali metals?

In molten salts, lithium exhibits unique behavior compared to other alkali metals. Its small size and high charge density allow for stronger interactions with the salt anions, resulting in different solubility, conductivity, and electrochemical properties in molten salt systems.

52. Why does lithium form more stable complexes with nitrogen-containing ligands compared to other alkali metals?

Lithium forms more stable complexes with nitrogen-containing ligands due to its high charge density and small size. These properties allow for stronger interactions with the lone pair electrons of nitrogen, resulting in more stable coordination compounds compared to larger alkali metals.

53. Why does lithium have a higher specific strength (strength-to-weight ratio) compared to other alkali metals?

Lithium has a higher specific strength due to its low density combined with relatively strong metallic bonding. The small size and high charge density of lithium atoms result in stronger interatomic forces relative to its mass, leading to a higher strength-to-weight ratio compared to other alkali metals.

54. Why does lithium have a higher electrochemical potential compared to other alkali metals?

Lithium has the highest electrochemical potential among alkali metals due to its small size and high ionization energy. These properties make it energetically favorable for lithium to lose an electron, resulting in a more positive standard reduction potential compared to other alkali metals.