Anomalous Behaviour of Beryllium

Edited By Shivani Poonia | Updated on Jul 02, 2025 06:04 PM IST

Imagine certain situations whereby you need your material strong, yet light, corrosive-resistant, and resistant to high temperatures. Obviously, at no time is such material coming at a free cost into being. This material, beryllium, very vital in the engineering industry, like aerospace, where every gram counts, and the electronics industry because it deals with durability. Although beryllium, due to its position within Group 2 of the Periodic Table, is an alkaline earth metal by definition, some of its properties may differ appreciably from those of other family members in the same column, that is, magnesium and calcium. Deviation from this type of behavior is called anomalous behavior.

This Story also Contains

Properties of Beryllium
Understanding the Anomalous Behavior of Beryllium
Some Solved Examples

Anomalous Behaviour of Beryllium

Berylium differs from the rest of the alkaline earth metals on account of its small atomic size, high electronegativity, and a slight difference in electronic configuration. Be²⁺ is very small. It exerts a high polarising effect on any anion associated with it. On account of this, beryllium compounds show a covalent character. Its compounds have low melting points and are soluble in organic solvents. These are hydrolyzed in water.

Properties of Beryllium

It is the hardest of all alkaline earth metals.
The melting and boiling points of the beryllium are the highest.
It is not affected by the atmosphere.
It does not decompose water.
It has the tendency to form covalent compounds
It does not react directly with hydrogen.
It dissolves in alkalies with the evolution of hydrogen.
It does not liberate hydrogen from acids readily.
Its oxide is amphoteric in nature.
Its hydroxide is amphoteric in nature.
Its carbide on hydrolysis evolves methane.
Its carbonate is not stable towards heat.
Its sulphate is soluble in water.
BeCl₂ is a covalent compound.
It has a strong tendency to form complex compounds.
It has a tendency to form alloys.

Understanding the Anomalous Behavior of Beryllium

Beryllium, atomic number 4, is a member of the periodic table Group 2: the alkaline earth metals. Be, though belonging to this group in the Periodic Table, shows most of its properties to be very different from its congeners: magnesium, calcium, strontium, Ba, and radium, Ra.

The deviation arises due to:

Relatively High Electronegativity
Small atomic and ionic size
High Ionization Energy

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Characteristics and Examples of Anomalous Behavior of Beryllium

The bond cannot be ionic with equal sharing of electrons because it is impossible for beryllium due to its small size and high charge of. This turns out to be another striking feature of its anomalous behavior. While MgCl₂and CaCl₂ can be the usual examples of ionic compounds, beryllium chloride itself is actually a covalent polymer. The covalency extends to its compounds with other elements too. Even the hydride of beryllium consists of structures that are polymeric rather than just mere simple ionic compounds.

The following are some of the key examples:

Beryllium Chloride, BeCl₂: The chloride is a covalent polymeric structure rather than being an example of a simple ionic compound.

Beryllium Hydride, BeH₂: The hydride also forms polymeric structures.

Beryllium Oxide, BeO: The oxide is amphoteric, and dissolves both in acids and bases to give beryllium salts and beryllates, respectively.

Importance and Uses in Various Fields of the Anomalous Property of Beryllium

Such anomalous behavior of beryllium plays a vital role both in academics and practical applications.

This anomalous behavior of beryllium helps the academic chemist about how atomic size and ionization energy in atoms affect chemical bonding.
Nuclear Reactors Used as neutron moderator and reflector.
Draws the attention of the aerospace industry for aircraft and spacecraft parts since it is a light metal with high strength, and hence is an ideal metal to be used for their construction.

Frequently Asked Questions (FAQs)

1. How does the size of beryllium compare to other elements in its group?

Beryllium is significantly smaller than other elements in its group. This is due to its low atomic number and high effective nuclear charge, which pulls the electrons closer to the nucleus, resulting in a smaller atomic radius.

2. What is the impact of beryllium's small size on its chemical properties?

Beryllium's small size leads to a high charge density, which results in a strong polarizing effect on nearby ions or molecules. This causes beryllium to form covalent bonds rather than ionic bonds, unlike other alkaline earth metals.

3. How does beryllium's electronegativity compare to other alkaline earth metals?

Beryllium has a higher electronegativity than other alkaline earth metals. This is due to its smaller size and higher effective nuclear charge, which allows it to attract electrons more strongly in chemical bonds.

4. What is the oxidation state of beryllium in its compounds?

Beryllium typically has an oxidation state of +2 in its compounds, like other alkaline earth metals. However, due to its covalent nature, the charge is often not a full +2 but is shared between beryllium and the other elements in the compound.

5. How does beryllium's melting point compare to other group 2 elements?

Beryllium has a much higher melting point compared to other group 2 elements. This is due to the strong covalent bonding in its solid state, which requires more energy to break than the metallic bonding in other alkaline earth metals.

6. Why is beryllium considered anomalous among the alkaline earth metals?

Beryllium is considered anomalous because it behaves differently from other elements in its group. This is due to its small size, high charge density, and high polarizing power, which lead to covalent bonding rather than ionic bonding typical of other alkaline earth metals.

7. How does the electron configuration of beryllium contribute to its anomalous behavior?

Beryllium's electron configuration (1s² 2s²) contributes to its anomalous behavior. The fully filled 2s orbital is relatively stable, making it difficult to remove electrons and form ionic bonds. This leads to covalent bonding and other unique properties.

8. Why does beryllium form covalent compounds instead of ionic ones?

Beryllium forms covalent compounds due to its high ionization energy and small size. The energy required to remove electrons is too high, making it energetically unfavorable to form ionic bonds. Instead, it shares electrons to form covalent bonds.

9. Why doesn't beryllium react with water, unlike other alkaline earth metals?

Beryllium doesn't react with water because it forms a protective oxide layer on its surface. This layer prevents further reaction with water. Additionally, the high energy required to remove electrons from beryllium makes it less reactive than other alkaline earth metals.

10. How does beryllium behave in aqueous solutions?

In aqueous solutions, beryllium forms complex ions rather than simple hydrated ions like other alkaline earth metals. It often forms tetrahedral [Be(H2O)4]2+ complexes due to its high polarizing power and tendency for covalent bonding.

11. What is the reason for beryllium's diagonal relationship with aluminum?

Beryllium shows a diagonal relationship with aluminum due to similarities in their charge/radius ratio. This results in similar chemical properties, such as the formation of amphoteric oxides and the tendency to form covalent compounds.

12. Why does beryllium form a stable carbonate, unlike other alkaline earth metals?

Beryllium forms a stable carbonate (BeCO3) because of the covalent nature of the Be-O bonds. This makes it less susceptible to thermal decomposition compared to the ionic carbonates of other alkaline earth metals.

13. Why does beryllium not form a stable peroxide like other alkaline earth metals?

Beryllium does not form a stable peroxide because its small size and high charge density make it difficult to accommodate the large peroxide ion. Additionally, the covalent nature of beryllium compounds doesn't favor the ionic structure typical of peroxides.

14. Why does beryllium not react with nitrogen directly, unlike other group 2 elements?

Beryllium does not react directly with nitrogen because of the high activation energy required to break the strong N≡N triple bond. The small size and high ionization energy of beryllium make it energetically unfavorable to form ionic nitrides.

15. How does the behavior of beryllium chloride in organic solvents differ from other alkaline earth metal chlorides?

Beryllium chloride is soluble in organic solvents and exists as a covalent molecule (BeCl2), unlike other alkaline earth metal chlorides which are typically ionic and insoluble in organic solvents. This is due to beryllium's tendency to form covalent bonds.

16. Why does beryllium form a covalent fluoride (BeF2) while other alkaline earth metals form ionic fluorides?

Beryllium forms a covalent fluoride (BeF2) due to its small size and high charge density, which lead to a high degree of polarization of the fluoride ions. Other alkaline earth metals are larger and form more ionic bonds with fluorine.

17. How does the reactivity of beryllium with acids compare to other group 2 elements?

Beryllium is less reactive with acids compared to other group 2 elements. This is due to the formation of a protective oxide layer on its surface and its higher ionization energy, which makes it more difficult to lose electrons.

18. Why does beryllium not form a stable hydride like other alkaline earth metals?

Beryllium does not form a stable hydride because its small size and high charge density make it difficult to accommodate the hydride ion. Additionally, the covalent nature of beryllium bonding doesn't favor the ionic structure typical of alkaline earth metal hydrides.

19. Why does beryllium form tetrahedral complexes instead of octahedral ones like other alkaline earth metals?

Beryllium forms tetrahedral complexes due to its small size and sp3 hybridization. The tetrahedral geometry allows for optimal spacing of ligands around the small beryllium atom, while larger alkaline earth metals can accommodate more ligands in an octahedral arrangement.

20. How does the basicity of beryllium oxide compare to other alkaline earth metal oxides?

Beryllium oxide is less basic compared to other alkaline earth metal oxides. It exhibits amphoteric behavior, able to react with both acids and bases. This is due to the covalent nature of the Be-O bond and beryllium's high polarizing power.

21. Why does beryllium not form a stable sulfate like other group 2 elements?

Beryllium does not form a stable sulfate because its small size and high charge density lead to extensive hydrolysis in aqueous solutions. Instead of forming a stable sulfate, beryllium tends to form complex hydroxyl species in water.

22. How does the tendency to form organometallic compounds differ between beryllium and other alkaline earth metals?

Beryllium has a greater tendency to form organometallic compounds compared to other alkaline earth metals. This is due to its smaller size and higher electronegativity, which allow it to form stronger covalent bonds with carbon atoms.

23. Why does beryllium not readily participate in redox reactions like other group 2 elements?

Beryllium does not readily participate in redox reactions because of its high ionization energy and the stability of its +2 oxidation state. The energy required to remove additional electrons or reduce Be2+ is too high under normal conditions.

24. Why does beryllium form more stable complexes with nitrogen-containing ligands compared to oxygen-containing ones?

Beryllium forms more stable complexes with nitrogen-containing ligands due to the better orbital overlap between beryllium and nitrogen. The similar sizes of Be and N atoms allow for stronger covalent bonding compared to the larger oxygen atom.

25. How does the thermal stability of beryllium compounds compare to those of other group 2 elements?

Beryllium compounds often have higher thermal stability compared to similar compounds of other group 2 elements. This is due to the stronger covalent bonding in beryllium compounds, which requires more energy to break.

26. Why does beryllium not form a stable nitrate like other alkaline earth metals?

Beryllium does not form a stable nitrate because its small size and high charge density lead to extensive hydrolysis in aqueous solutions. Instead of forming a stable nitrate, beryllium tends to form complex hydroxyl species in water.

27. How does beryllium's hydration energy compare to other group 2 elements?

Beryllium has a much higher hydration energy compared to other group 2 elements. This is due to its small size and high charge density, which allows it to attract water molecules more strongly, forming strong hydration shells.

28. What is the hybridization of beryllium in its compounds?

Beryllium typically exhibits sp3 hybridization in its compounds. This allows it to form four covalent bonds, often resulting in tetrahedral geometry around the beryllium atom.

29. Why does beryllium form polymeric structures in many of its compounds?

Beryllium forms polymeric structures due to its small size and high charge density, which allow it to form bridge bonds between molecules. This results in extended network structures rather than discrete molecular units.

30. How does the reactivity of beryllium compare to other group 2 elements?

Beryllium is generally less reactive than other group 2 elements. This is due to its higher ionization energy, stronger covalent bonding, and the formation of a protective oxide layer on its surface.

31. How does beryllium oxide (BeO) differ from other alkaline earth metal oxides?

Beryllium oxide (BeO) is different from other alkaline earth metal oxides in several ways. It has a higher melting point, is less soluble in water, and exhibits amphoteric behavior. These properties are due to the covalent nature of the Be-O bond.

32. Why is beryllium hydroxide amphoteric?

Beryllium hydroxide is amphoteric because it can act as both an acid and a base. This is due to beryllium's small size and high polarizing power, which allow it to donate or accept protons depending on the reaction conditions.

33. How does the coordination number of beryllium compare to other alkaline earth metals?

Beryllium typically has a coordination number of 4, while other alkaline earth metals often have higher coordination numbers (6 or 8). This is due to beryllium's small size, which limits the number of ligands that can surround it.

34. Why does beryllium form stable complexes with organic ligands?

Beryllium forms stable complexes with organic ligands due to its high charge density and tendency for covalent bonding. These properties allow it to form strong coordinate covalent bonds with electron-rich ligands like ethylenediamine or acetylacetone.

35. Why is beryllium carbide (Be2C) different from other alkaline earth metal carbides?

Beryllium carbide (Be2C) is different because it has a covalent structure, unlike the ionic carbides formed by other alkaline earth metals. When hydrolyzed, it produces methane instead of acetylene, which is typical for ionic carbides.

36. How does the solubility of beryllium salts compare to other group 2 element salts?

Beryllium salts are generally less soluble than those of other group 2 elements. This is due to the covalent nature of beryllium compounds and the strong lattice energy in its solid structures.

37. How does beryllium's first ionization energy compare to other group 2 elements?

Beryllium has a significantly higher first ionization energy compared to other group 2 elements. This is due to its small size and the stability of its fully filled 2s orbital, making it more difficult to remove an electron.

38. How does the crystal structure of metallic beryllium differ from other alkaline earth metals?

Metallic beryllium has a hexagonal close-packed (hcp) crystal structure, while other alkaline earth metals typically have body-centered cubic (bcc) or face-centered cubic (fcc) structures. This difference is due to beryllium's smaller size and stronger covalent character.

39. How does the electron affinity of beryllium compare to other group 2 elements?

Beryllium has a lower electron affinity compared to other group 2 elements. This is because its 2s orbital is fully filled, making it less favorable to accept an additional electron. This contributes to beryllium's tendency to form covalent rather than ionic bonds.

40. How does the lattice energy of beryllium compounds compare to those of other alkaline earth metals?

Beryllium compounds generally have higher lattice energies compared to similar compounds of other alkaline earth metals. This is due to beryllium's small size and high charge density, which lead to stronger electrostatic interactions in the crystal lattice.