9.
Explanation
Beryllium (Be) exhibits several anomalous behaviors compared to other elements in the periodic table, primarily due to its small atomic size and unique electronic configuration. Here are some key points highlighting the anomalous behavior of beryllium:
1.Small Atomic Size: Beryllium is the second-lightest element in Group 2 (alkaline earth metals) of the periodic table. Its small atomic size results in several distinctive features:
- High Ionization Energy: Beryllium has a higher ionization energy compared to other Group 2 elements. It requires more energy to remove an electron from a beryllium atom due to its small size.
- Small Covalent Radius: Beryllium forms shorter covalent bonds than expected, reflecting its small covalent radius.
3. Absence of Diagonal Relationship: While other Group 2 elements exhibit diagonal relationships with elements in different groups (e.g., Be with Al), beryllium lacks this pattern due to its unique properties. Diagonal relationships usually involve similarities in size, charge, and chemistry between elements in diagonally related positions on the periodic table.
4. Limited Covalent Chemistry: Beryllium’s small size and high ionization energy result in limited covalent chemistry compared to its group members. It typically forms covalent compounds with electronegative elements like oxygen, such as beryllium oxide (BeO), which is amphoteric.
5. No S-Orbital Overlap: In many compounds, beryllium forms only two bonds because it lacks the available d orbitals for hybridization. This results in linear geometries, which is observed in compounds like BeCl2.
6. Brittle Nature: Beryllium and its compounds are exceptionally brittle, and they do not follow the typical metallic properties of malleability and ductility. This brittleness is attributed to the strong directional covalent bonds in its crystal lattice.
7. Limited Aqueous Chemistry: Unlike other Group 2 elements, beryllium forms poorly soluble hydroxides and sulfates. Its hydroxide, Be(OH)2, is amphoteric and reacts differently in aqueous solutions compared to the hydroxides of its group members.
8. Toxicity: Beryllium and its compounds are highly toxic, and inhalation of beryllium dust or vapor can lead to a lung condition known as berylliosis. This toxicity is due to its high chemical reactivity in the body.
In summary, the anomalous behavior of beryllium can be attributed to its small atomic size, high ionization energy, limited covalent bonding capacity, and unique chemical properties. These characteristics set beryllium apart from its group members and lead to distinct behavior in terms of chemistry and reactivity.