The general electronic configuration of the transition elements is

• (n-1)d¹⁰, (n+1)s²

• (n- 1)d^1-10, (n + 1)s^1-2

• (n- 1)d^1-10, np⁶,ns²

• (n- 1)d^1-10, ns^1-2

Which of the following ions is colourless in solution?

• V³⁺

• Cr³⁺

• Co²⁺

• Sc³⁺

Most common oxidation states of Ce (cerium) are

• +3, +4

• +2, +3

• +2, +4

• +3, +5

Most basic hydroxide among the following is

• Lu(OH)₃

• Eu(OH)₃

• Yb(OH)₃

• Ce(OH)₃

Most common oxidation states shown by cerium are

• +2, +4

• +3, +4

• +3, +5

• +2, +3

Which gives + 7 oxidation state ?

• Mn(25)

• Cr (24)

• Cu(29)

• Fe(26)

Which of the following transitions involves maximum amount of energy?

• ${{\mathrm{M}}^{-}}_{\left(\mathrm{g}\right)\hspace{0.17em}}\to {\mathrm{M}}_{\left(\mathrm{g}\right)}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{+}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)}^{+} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{2+}$

• ${\mathrm{M}}_{\left(\mathrm{g}\right)}^{2+} \to {\mathrm{M}}_{\left(\mathrm{g}\right)}^{3+}$

68.

Select the coloured compound amongst the following .

(At. no. Ti= 22, Cr= 24, Cu= 29, Zn= 30)

• TiCl₄

• CrCl₃

• ZnCl₃

• CuCl

The only radioactive element among the lanthanoids is

• gadolinium

• holmium

• promethium

• neodymium

Identify a 'chemical twin' among the following.

• Zr-Ta

• Nb-Tc

• Hf-Re

• Nb-Ta