Question

Diagonal relationship between beryllium and aluminium?

Answer 1

Diagonal relationship of Be with Al Because of its small size Be differs from other earth alkaline earth metals but resembles in many of its properties with Al on account of diagonal relationship.          (1) Be2+ and Al3+ have almost same and smaller size and thus favour for covalent bonding.           (2) Both these form covalent compounds having low melting point and soluble in organic solvent.      (3) Both have same value of electronegativity (which is 1.5).          (4) The standard O.P of these elements are quite close to each other ; Be2+=1.69 volts and Al3+= 1.70 volts.          (5) Both become passive on treating with concentrated HNO3 in cold.          (6) Both form many stable complexes for example (BeF3)-, (AlH4)-.          (7) Like BeO, Al2O3 is amphoteric in nature. Also both are high melting point solids.          Al2O3 + 2NaOH → 2NaAlO2 + H2O          Al2O3 + 6HCl → 2AlCl3 + 3H2O          (8) Be and Al both react with NaOH to liberate H2 forming beryllates and alluminates.             Be + 2NaOH → Na2BeO2+H2             2Al + 6NaOH → 2Na3AlO3 + 3H2          (9) Be2 C and Al4C3 both provides CH4 on treating with the water.             Be2C+ 2H2O → CH4 + 2BeO             Al4C3 + 6H2O → 3CH4 + 2Al2O3           (10) These both occur together in the nature in the ore of beryl, 3BeO. Al2O3. 6SiO2.          (11) Unlike other alkaline earths but such as aluminium, beryllium is not effortlessly attacked by air (Also Mg is not attacked by the air)          (12) Both Be and Al react very slowly with dilute HCl to liberate H2.          (13) Both Be and Al form polymeric covalent hydrides while hydrides of other alkaline earth are ionic.          (14) BeCl2 and AlCl3 are both prepared is the similar way.             BeO+ C+ Cl2  → BeCl2 + CO              Al2O3 + 3C +3Cl2 → 2AlCl3 + 3CO          (15) Both BeCl2 and AlCl3 are soluble in organic solvents and act as catalyst in Friedel -Crafts reaction.          (16) Be (OH)2 and Al (OH)3 are both amphoteric whereas hydroxides of other alkaline earths are  strong alkali.          (17) The salts of Be and Al are extensively hydrated.          (18) BeCl2 and AlCl3 both have a bridged polymeric structure.          (19) Be and Al both form fluoro complex ions [BeF4]2- and [AlF6]3- in solution state whereas other members of 2nd group do not form such complexes.

Answer 2

Explanation:

1. both the metals have the tendency to form covalent compounds