Boron does not form `[BF_6]^(3-)` whereas `[AlF_6]^(2-)` exists, why?

Li and Mg belonging to first and second group in periodic table respectively resemble each other in many respects. a) Name the relationship. b) B can only form [BF_4]^- ion while Al can form [AlF_6]^3- though both B and Al belong to group 13. Justify.

Boron chloride do not form dimers where as Aluminium chloride exist as dimers. Do you agree with this statement? Substantiate your answer.

Boron, Aluminium, Gallium, Indium and Thallium belong to group 13 of the periodic table of elements. While Aluminium can be form the ion [AIF_6]^(3-) , Boron is unable to form [BF_6]^(3-) ion. Explain.

SiCl_4' forms '[SiCl_6]^(2-)' while 'CCl_4' does not form '[CCl_6]^(2-)]' Explain.

Assertion : [Fe(H_2O)_6]^(3+) is strongly paramagnetic whereas [Fe(CN)_6]^(3-) is weakly paramagnetic. Reason : H_2O is a weak field ligand and CN^(-) is a strong field ligand.

[Fe(H_2O)_6]^(3+) is strongly paramagnetic whereas {Fe(CN)_6]^(3-) is weakly paramagnetic Expain?

[Co(NH_3)_6]^3+ is an inner orbital complex whereas [Ni(NH_3)_6]^(2+) is an outer orbital complex.Explain.

Which statement is incorrect? (1) Boron exist in many allotropic forms with B 12 icosahedral units (2) The most abundant metal is present in cyolite and bauxite (3) Gallium exist as a liquid metal on a warm day (4) Boron compounds are electron sufficient

Why AlCl_3 exist as dimers?