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Coordination Compounds — Chemistry STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryCoordination Compounds3 Marks
Question
Define the following terms: (1) Coordination entity (2) Central atom / ion.
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Answer

(1) Coordination entity:
→ "A coordination entity constitutes a central metal atom or ion bonded to a fixed number of ions or molecules."
→ For example, $\left[ CoCl _3\left( NH _3\right)_3\right]$ is a coordination entity in which, the cobalt ion is surrounded by three ammonia molecules and three chloride ions.
→ Other examples are $\left[ Ni ( CO )_4\right],\left[ PtCl _2\left( NH _3\right)_2\right]$, $\left[ Fe ( CN )_6\right]^{4-}$ and $\left[ Co \left( NH _3\right)_6\right]^{3+}$
(2) Central atom/ion:
→ "In a coordination entity, the atom/ion to which a fixed number of ions/groups are bound in a definite geometrical arrangement around it, is called the central atom or ion."
→ For example, the central atom/ion in the coordination entities:
Co-ordination
entities		Central atom / ion
$\left[ NiCl _2\left( H _2 O \right)_4\right]$$Ni ^{2+}$
$\left[ CoCl \left( NH _3\right)_5\right]^{2+}$$Co ^{3+}$
$\left[ Fe ( CN )_6\right]^{3-}$$Fe ^{3+}$

→ These central atoms/ions are also referred to as Lewis acids.

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