Coordination Compounds

In the chromate ion (CrO4^2-), oxygen has an oxidation number of -2. Since there are 4 oxygen atoms contributing -8 total and the ion has a -2 charge, the chromium must be +6 to balance: +6 + (-8) = -2.

Hemoglobin contains iron (Fe) in its heme group, specifically in the +2 oxidation state (Fe(II) or Fe^2+). This iron center is what allows hemoglobin to bind and transport oxygen in the blood.

For stable complex formation, ligands should have LOW ionization enthalpy (they need to easily donate electron pairs to form coordinate bonds). High ionization enthalpy would make it difficult for ligands to act as Lewis bases and donate electrons to the central metal ion.

Chloride ion (Cl^-) has the maximum lone pairs - it has 4 lone pairs (8 electrons) in its valence shell. H^- has 1 lone pair, H2O has 2 lone pairs, and NH3 has 1 lone pair. All these are monodentate ligands.

This statement is INCORRECT because chelates with five-membered rings are generally MORE stable than those with double bonds (which can introduce strain and reactivity). Chelates with saturated five-membered rings are actually among the most stable configurations.

Ionisation isomerism occurs when compounds have the same composition but give different ions in solution. This happens when the counter ion and ligand exchange places, changing which species dissociate into ions when dissolved.

KNaCO3 (potassium sodium carbonate) is a double salt. Double salts are compounds that contain two different cations that crystallize together in a fixed ratio. The other options are simple single-cation salts.

In [Pt(en)(H2O)2(NO2)(Cl)]^2+: ethylenediamine (en) is neutral (0), each H2O is neutral (0), NO2^- is -1, Cl^- is -1, and the overall charge is +2. So: Pt + (0) + (0+0) + (-1) + (-1) = +2, therefore Pt = +4.

Geometrical isomerism requires restricted ligand arrangement with cis/trans positioning. Tetrahedral complexes (CN=4) never show it because all ligands are adjacent. Linear (CN=2) and trigonal planar (CN=3) geometries lack the spatial arrangement needed. Square planar (CN=4) and octahedral (CN=6) complexes do show geometrical isomerism.

In coordination compounds, donor atoms are ligand atoms that directly coordinate to the central metal ion. In [Co(NH3)6]Cl3, ammonia (NH3) ligands coordinate through nitrogen atoms. Chlorine is outside the coordination sphere as a counterion.

Optical activity requires non-superimposable mirror images (chirality). [Co(NH3)6]Cl3 has six identical ammonia ligands in octahedral geometry with perfect symmetry - it has multiple planes and axes of symmetry, making it achiral. The other compounds have asymmetric arrangements.

Coordination compounds are distinct entities that don't dissociate into original components in solution. They behave as single units with unique properties different from constituent simple compounds. Option C incorrectly suggests they dissociate like simple salts.

Coordination number is the number of donor atoms directly bonded to the central metal ion. In [Ag(NH3)2]+, two ammonia ligands coordinate to silver, each through one nitrogen atom, giving CN=2.

Optical activity (chirality) requires absence of improper rotation axes including mirror planes. Square planar complexes inherently possess at least one molecular plane - the plane of the complex itself acts as a symmetry plane, making them achiral.

The oxalate ion (C2O4)2- is a bidentate ligand, coordinating through two oxygen atoms. In [Cr(C2O4)3]3-, three oxalate ligands each donate two electron pairs, giving 3×2=6 donor atoms bonded to chromium, so CN=6.

Geometrical isomerism is a subtype of stereoisomerism where isomers differ in spatial arrangement but not in bonding connectivity. Geometrical isomers have different physical properties. Cis-isomers have identical ligands adjacent; trans-isomers have them opposite.

EDTA is a hexadentate ligand that wraps around the metal ion. In [Co(edta)]-, EDTA occupies all six coordination sites in octahedral geometry. This arrangement creates a chiral center, giving two enantiomers (optical isomers).

Coordination isomerism occurs in compounds containing both cationic and anionic complex species where ligands can redistribute between the metal centers in cation and anion. This creates different isomers based on ligand distribution.

Stereoisomerism has two main types: geometrical isomerism (cis/trans, fac/mer) and optical isomerism (enantiomers). All stereoisomers fall into these two categories based on how they differ spatially.

CoCl3·6NH3 is [Co(NH3)6]Cl3. In solution, it dissociates into [Co(NH3)6]3+ cation and 3 Cl- anions, giving 4 total ions. Conductance measurements reveal this ionic composition, showing the coordination sphere remains intact.

Fe(CO)5 is iron pentacarbonyl, a neutral coordination complex. With five CO ligands around a central metal ion, the only stable geometry that minimizes repulsion while satisfying the 18-electron rule is trigonal bipyramidal. Square planar would require only 4 ligands, tetrahedral geometry with 5 ligands is unstable, and trigonal planar only accommodates 3 ligands.

CoCl3.4NH3 dissociates in water to give [Co(NH3)4Cl2]+ and Cl- ions, totaling 2 ions per formula unit. Conductance measurements directly count the number of ions produced, not the coordination number. The compound exists as [Co(NH3)4Cl2]Cl, where the complex cation and one chloride ion separate in solution.

Linkage isomerism occurs when ambidentate ligands can bind through different donor atoms. The nitrite ion (NO2-) is a classic ambidentate ligand that can bind through nitrogen (nitro: -NO2) or through oxygen (nitrito: -ONO). The two complexes [Co(NH3)5ONO]2+ and [Co(NH3)5NO2]2+ differ only in which atom binds to cobalt, making them linkage isomers.