In Cu-ammonia complex, the state of hybridisation of Cu²⁺ is

• sp³

• d³s

• sp²f

• dsp²

What is the correct electronic configuration of the central atom in K₄[Fe(CN)₆] based on crystal field theory

• ${\mathrm{t}}_{2\mathrm{g}}^6{\mathrm{e}}_{\mathrm{g}}^0$

• ${\mathrm{e}}^3{\mathrm{t}}_2^3$

• ${\mathrm{e}}^4{\mathrm{t}}_2^2$

• ${\mathrm{t}}_{2\mathrm{g}}^4 {\mathrm{e}}_{\mathrm{g}}^2$

Which of the following species is not stable?

• [GeCl₆]^2-

• [Sn(OH)₆]^2-

• [SiCl₆]^2-

• [SiF₆]^2-