The sums of the first and second, and of the third and fourth ionisation energies of nickel and platinum are: | | IE₁+IE₂ (MJ mol⁻¹) | IE₃+IE₄ (MJ mol⁻¹) | | Ni | 2.49 | 8.80 | | Pt | 2.66 | 6.70 | i) Give the most common oxidation state of Ni and of Pt, with reason. ii) Name the metal (Ni or Pt) which forms compounds in the +4 state more easily, and why.

(i) Ni: +2 (lower IE₁+IE₂); Pt: +4 (its IE₃+IE₄ is comparatively low). (ii) Pt — IE₃+IE₄ of Pt (6.70) ≪ that of Ni (8.80).

CBSE Class 12 · 2000 · Delhi · d and f Block ElementsShort Answer

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The sums of the first and second, and of the third and fourth ionisation energies of nickel and platinum are:

	IE₁+IE₂ (MJ mol⁻¹)	IE₃+IE₄ (MJ mol⁻¹)
Ni	2.49	8.80
Pt	2.66	6.70

i) Give the most common oxidation state of Ni and of Pt, with reason.
ii) Name the metal (Ni or Pt) which forms compounds in the +4 state more easily, and why.

Solution

(i) Ni: IE

_{1}

+IE

_{2}

(2.49) is lower for Ni than Pt, so Ni

^{2 +}

forms easily — the most common state of nickel is +2.
Pt: its IE

_{3}

+IE

_{4}

(6.70) is much lower than nickel's, so platinum readily reaches +4 — the common state of Pt is +4 (as in PtCl

_{4}

, [PtCl

_{6}

]

^{2 -}

).
(ii) Platinum: the energy needed for the 3rd + 4th ionisations is far smaller for Pt (6.70 MJ mol

^{- 1}

) than for Ni (8.80), so Pt forms +4 compounds much more easily.

CBSE Class 12 Board · 2000 · Delhi · Subjective

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CBSE Class 12 · 2000 · Delhi · d and f Block ElementsShort Answer

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