Anomalous Behavior of Beryllium

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Periodic table‘s first element, beryllium (Be), belongs to Group 2 (alkaline earth metals), and it differs greatly from the other elements in its group in a few key ways. We call this phenomena the “anomalous behavior of beryllium.” Beryllium is unique among alkaline earth metals despite their overall similarities.
Its small atomic and ionic size, high ionization energy, high electronegativity, and lack of a d-orbital set it separately.  Beryllium, varies from heavier kind like magnesium, calcium, strontium, barium, and radium.
Anomalous Behavior of Beryllium-Metals

Causes of Anomalous Behavior of Beryllium

Main factors responsible for the unique properties of beryllium are:-
1.Small Atomic and Ionic Size: Due to its modest ionic radius (31 pm) and atomic radius (112 pm), beryllium has a high charge density. Because of this, beryllium’s bonding behavior is less like that of other metals in its group and more like that of some non-metals or metalloids, such as aluminum.
2. High Ionization Energy: Compared to other alkaline earth metals, beryllium has a substantially greater ionization energy (899.5 kJ/mol). Its small size and strong nuclear charge, Firmly retains the electrons and makes them difficult to release, are the causes of this. Hence, unlike its heavier cousins, beryllium prefers to form covalent connections as opposed to ionic ones.
3. High Electronegativity: Compared to other Group 2 elements, beryllium has a higher electronegativity (1.57 on the Pauling scale). While other alkaline earth metals mostly form ionic compounds, its high electronegativity also plays a role in its tendency to create covalent compounds.
4. Absence of d-Orbitals: Because, its valence shell does not contain any unoccupied d-orbitals, beryllium cannot have more than four coordination numbers. In comparison, the other alkaline earth metals can create complexes with larger coordination numbers by using their d-orbitals.

Demonstration of Anomalous Behavior of Beryllium

1.Compared to other alkaline earth metals, beryllium has a number of special qualities because of the above stated reasons. Its bonding nature, solubility, and reactivity are only a few of the chemical and physical properties that show these variations.
2. Formation of Covalent Compounds: Beryllium tends to form covalent compounds, whereas the majority of alkaline earth metals produce primarily ionic compounds. For example, in the solid state, beryllium chloride (BeCl₂) exists as a covalent polymer, whereas in the gas phase, it forms linear BeCl₂ molecules. On the other hand, ionic structures are formed by magnesium chloride (MgCl₂) and other chlorides of alkaline earth metals.
3.Low Tendency to Form Basic Oxides: Beryllium oxide (BeO) reacts with both acids and bases, it is an amphoteric substance. Other alkaline earth metal oxides, including calcium oxide (CaO), on the other hand, have very basic oxides. Another effect of beryllium’s increased electronegativity and covalent nature is its amphoteric tendency.
4.Non-Participation in Redox Reactions: Participation of beryllium in redox processes is difficult. Because of its high ionization energy, beryllium is less likely to undergo such oxidation than other alkaline earth metals, which are easily able to shed two electrons to produce +2 oxidation state ions. It is hence less reactive with water and air
5. Resistance to Acid Attack: Beryllium does not react with hydrochloric acid (HCl) to release hydrogen gas, in compare to other alkaline earth metals. An oxide layer (BeO) has formed on the metal’s surface to shield it from further reaction, the metal is resistant to acid assault. But in non-oxidizing acids like sulfuric acid (H₂SO₄), beryllium dissolves and forms beryllium sulfate (BeSO₄).
6 Formation of Complex Compounds: Complex compounds are formed by beryllium more easily than other elements in Group 2. For example, magnesium does not form such complexes, but beryllium hydroxide [Be(OH)₂] dissolves in sufficient alkali to generate beryllate ion [Be(OH)₄²⁻].
7. Diagonal Relationship with Aluminum: A “diagonal relationship” has been found between beryllium and aluminum, indicating that the two elements of Group 13 have comparable chemical behaviors.
Aluminum and beryllium are both amphoteric, form covalent compounds, and have comparable tendencies toward complex formation. For example, with excess alkali, Be(OH)₂ and Al(OH)₃ dissolve to produce, respectively, beryllate [Be(OH)₄²⁻] and aluminate [Al(OH)₄⁻] ions.

Note:-

Due to its small size, high ionization energy, high electronegativity, and lack of d-orbitals, beryllium shows abnormal behavior. Because of these properties, beryllium behaves more like a metalloid or non-metal, mostly generating complex ions, amphoteric oxides, and covalent compounds.
The characteristics are different from those of the other elements in Group 2, like calcium, magnesium, and barium, show basic oxides and produce more ionic compounds. The peculiar chemical behavior of beryllium within the periodic table is further highlighted by its diagonal interaction with aluminum.
Unlike other alkaline earth metals like magnesium and calcium, beryllium typically forms ionic compounds, such as beryllium hydroxide [Be(OH)₂] and beryllium chloride (BeCl₂).
Because beryllium oxide (BeO) reacts with both acids and bases, it is an amphoteric substance. Other Group 2 element oxides, such as calcium oxide (CaO), on the other hand, are strongly basic and do not behave in an amphoteric manner.
Because a protective oxide layer (BeO) forms on the surface of beryllium to thwart interactions with acids like hydrochloric acid, beryllium is immune to acid attack. Sulfuric acid is one non-oxidizing acid in which it does dissolve, though.
Because beryllium and aluminum have a diagonal relationship, although being in separate groups, they have similar chemical characteristics. Both combine to generate complex ions, amphoteric oxides, and covalent compounds such as aluminate [Al(OH)₄⁻] and beryllate [Be(OH)₄²⁻].
Because of its small atomic size and strong nuclear charge, which firmly keep its electrons and make them difficult to remove, beryllium has a high ionization energy. Its unusual behavior is mostly caused by this.
Unlike other Group 2 elements that can utilise their d-orbitals for complex formation, beryllium is limited to a coordination number of four due to the absence of its d-orbitals. This also limits its capacity to create complexes with greater coordination numbers.

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