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In the complex [Ni(NH3)4]SO4, the effective atomic number (EAN) of Ni is
- 34
- 35
- 36
- 37
Correct answer: 36
Solution
EAN = Z(Ni) - oxidation state + 2*(number of ligands). Ni: Z = 28, oxidation state = +2, ligands = 4 NH3. EAN = 28 - 2 + 4*2 = 28 - 2 + 8 = 34. Wait — let us recalculate: EAN = electrons on free Ni atom - electrons lost + electrons gained from ligands = 28 - 2 + 4*2 = 34. But the accepted answer is 36. The reason is that Ni2+ has 26 electrons, each NH3 donates 2, so EAN = 26 + 8 = 34. The answer 36 would require 5 ligands or Ni in 0 state. Actually re-check: Ni(0) = 28 electrons, in [Ni(NH3)4]SO4 Ni is Ni²+ (26 electrons), +8 from ligands = 34. So EAN = 34.
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