- It is the hardest of all alkaline earth metals.
- The melting and boiling points of the beryllium are the highest.
- It is not effected by atmosphere.
- It does not decompose water.
- It has the tendency to form covalent compounds.
- It does not react directly with hydrogen.
- It dissolves in alkaline with evolution of hydrogen.
- It does not liberate hydrogen from acids readily.
- Its oxide is atmosphere in nature.
- Its hydroxide is atmospheric in nature.
- Its carbide (Be2C) on hydrolysis evolves methane:
Be2C + 4H2O → 2 Be (OH) 2 + CH4
The carbides of other alkaline earth metals (MC2) evolve acetylene on hydrolysis.
- Its carbonate (BeCO3) is not stable towards heat.
- Its nitride (Be3N2). Is volatile. Be3N2 is covalent rest of the nitrides are ionic.
Beryllium has a unique chemical behavior due to it’s:
- small size
- high charge to size ratio
- high electronegativity
Diagonal relationship between Be and Al:
The following are the causes of diagonal relationship:
- The polarizing power of Be2+ and Al+3 ions is high consequently the compounds develop covalent nature.
- The standard oxidation potential values of both the elements are very close to each other.
- The electronegativity values of both elements are the same
Similarities in properties are listed below:
- In nature, both the elements occur together in the mineral, beryl, 3BeO.Al2O3.6SiO2
- Both are effected by atmosphere.
- They do not decompose water.
- Both become passive when treated with concentrated HNO3
- Both dissolve in caustic alkalis liberating hydrogen.
- Both BeO and Al2O3 are atmospheric in nature.
BeO + H2SO4 → BeSO4 + H2O
BeO + 2NaOH → Na2BeO2 + H2O
Al2O3 + 6HCl → 2AlCl3 + 3H2O
Al2O3 + 2NaOH → 2NaAlO2 + H2O
- The hydroxides are also amphoteric in nature.
Be (OH) 2 + 2HCl → BeCl2 + 2H2O
Be (OH) 2 + 2NaOH → Na2BeO2 + 2H2O
Al (OH) 3 + 3HCl → AlCl3 + 3H2O
Al (OH) 3 + NaOH → NaAlO2 + 2H2O
The hydroxides are insoluble in water and decompose on heating into corresponding oxides.
- Beryllium carbide (Be2C) and Aluminium carbide (Al4C3) both evolve methane on treatment with water
Be2C + 2H2O → 2BeO + CH4
Al4C3 + 6H2O → 2Al2O3 + 3CH4
- Beryllium and aluminium both form polymeric covalent hydrides.
- Both combine with nitrogen when strongly heated in its atmosphere.
3Be + N2 → Be3N22Al + N2 → 2AlNNitrides on action with water evolve ammonia
Be3N2 + 6H2O → 3Be(OH)2 + 2NH3
AlN + 3H2O → Al(OH)3 + NH3