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Why is it wrong to use the concept of hybridization for transition metal complexes?

Tetrahedral complexes Let's consider, for example, a tetrahedral $\ce{Ni(II)}$ complex ($\mathrm{d^8}$), like $\ce{[NiCl4]^2-}$. According to hybridisation theory, the central nickel ion has $\mathrm{...
orthocresol's user avatar
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57 votes
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Why isn't the American nickel magnetic?

There are many types of magnetic properties, including ferromagnetism, paramagnetism, diamagnetism, antiferromagnetism, ferrimagnetism, superparamagnetism, metamagnetism, spin glasses, and ...
theorist's user avatar
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25 votes
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What is the oxidation state of Mn in HMn(CO)5?

On negative oxidation states, in general Although it's usually a topic that's covered relatively late in a chemistry education, negative oxidation states for transition metals[1] are actually quite ...
orthocresol's user avatar
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25 votes

Why isn't the American nickel magnetic?

None of the US coins are magnetic (ferromagnetic), except for the 1943 Lincoln penny (Steel Cents, made in steel and zinc to save copper for ammunition during wartime), which are considered magnetic. ...
Mathew Mahindaratne's user avatar
24 votes
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Why is WF6 stable whereas CrF6 is unknown?

The answer has to do with two things. Note that HSAB theory is dubious at best and doesn't have very useful predictive power, so I am going to avoid talking about it. (1) The accessibility of the high ...
orthocresol's user avatar
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23 votes
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Why is manganese(II) coloured although the transition should be spin-forbidden?

Selection rules The intensity of the transition from a state $\mathrm{i}$ to a state $\mathrm{f}$ is governed by the transition dipole moment $\mu_{\mathrm{fi}}$ (strictly, it is proportional to $|\...
orthocresol's user avatar
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22 votes

Why isn't the orbital angular momentum also considered while calculating the magnetic moments 3d transition elements?

Simplistically speaking orbital angular momentum is present when some conditions are satisfied: A set of orbitals are degenerate; These orbitals can be "interconverted" by rotation about a certain ...
orthocresol's user avatar
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22 votes
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Why does the Co³⁺/Co²⁺ couple have such a high reduction potential?

The electronic configuration has nothing to do with it. The reduction potentials of $\ce{Ni^3+}/\ce{Ni^2+}$, $\ce{Cu^3+}/\ce{Cu^2+}$ and $\ce{Zn^3+}/\ce{Zn^2+}$, if they have been/could be measured, ...
orthocresol's user avatar
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17 votes
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Cr(II) and Mn(III) - their oxidizing and reducing properties?

Related question with same answer but in a different context of the 4f block: Why don't we see these lanthanide species? You have a misconception regarding the stability of oxidation states. The ...
orthocresol's user avatar
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17 votes

Exchange energy of d6 configuration

As @orthocresol points out, the key is that you need to compare the exchange energy before vs after the ionization process. Anything that is unchanged by ionization cannot affect ionization energy. ...
agaitaarino's user avatar
16 votes

Why is anhydrous copper(II) sulfate white while the pentahydrate is blue, even though both have one unpaired electron?

Let's compare the two compounds, here I plotted the $\ce{Cu(II)}$ centers of $\ce{CuSO4.5H2O}$ and $\ce{CuSO4}$ from their crystal structure data. As you can see, it changes from a $\ce{[Cu(H2O)4[SO4]...
Justanotherchemist's user avatar
16 votes

Why is Ni[(PPh₃)₂Cl₂] tetrahedral?

We sometimes call this type of complex 'pseudotetrahedral' since there is an isomerism from a tetrahedral to a square planar complex possible. I was unable to find the original work here but this link ...
Justanotherchemist's user avatar
15 votes
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While filling electrons, we follow Aufbau principle, but not while removing them. Why is this so?

Usually when adding electrons based on the Aufbau principle, you go from one element to the next highest one, e.g. from $\ce{Ti}: \ce{[Ar] 4s^2 3d^2}$ to $\ce{V: [Ar] 4s^2 3d^3}$. Thus you add not ...
Feodoran's user avatar
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14 votes
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Why can mercury(I) exist, but not zinc(I)?

On the contrary, zinc(I) compounds do exist, though they are rare, and relatively unstable. Most zinc(I) compounds contain a $\ce{[Zn2]^{2+}}$ core, which is analogous to the $\ce{[Hg2]^{2+}}$ cation. ...
ringo's user avatar
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13 votes
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What is the most common oxidation state of gold?

It's not obvious, but common oxidation state for gold is +3. It caused by destabilization of the $5d^{10}$ orbital. Detailed explanation you can find in The Chemistry of Gold, in Chapter 1.1.3.
Vadim Shkaberda's user avatar
13 votes
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Why is MnO2 not a peroxide?

Peroxides contain two oxygens connected by a single bond. X-ray or neutron diffraction will show that the oxygens in $\ce{MnO2}$ are too far apart to be bonded, and therefore it is not a peroxide. ...
Ian Bush's user avatar
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13 votes

Why is MnO2 not a peroxide?

The question’s logical premise is skewed. $\ce{CO2}$ is carbon(IV) oxide or carbon dioxide. But carbon(II) also exists and so does carbon(II) oxide (carbon monoxide, $\ce{CO}$). Just because there are ...
Jan's user avatar
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13 votes
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How do I find the ground state term symbol for transition metal complexes?

To find the ground state term symbol, you should be using symmetry and group theory arguments, you shouldn't have to resort to searching Tanabe-Sugano diagrams to get the answer. We'll start with ...
orthocresol's user avatar
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13 votes
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Derivation of the Orgel diagram for octahedral d2 complexes

1. Weak-field and strong-field limits I will adopt the description used in Figgis and Hitchman's Ligand Field Theory and Its Applications (p 5), because I cannot really phrase it better: It is ...
orthocresol's user avatar
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13 votes

Why is Ni[(PPh₃)₂Cl₂] tetrahedral?

Dichlorobis(triphenylphosphine)nickel(II), or $\ce{NiCl2[P(C6H5)3]2}$ in square planar form is red and diamagnetic. The blue form is paramagnetic and features tetrahedral Ni(II) centers. Both ...
Chakravarthy Kalyan's user avatar
12 votes
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How does aqua regia dissolve gold?

The wikipedia article of aqua regia has beautifully mentioned the mechanism of gold dissolving in aqua regia: Aqua regia dissolves gold, though neither constituent acid will do so alone, because, in ...
Nilay Ghosh's user avatar
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12 votes
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If the ferric ion is more stable than the ferrous ion, then why is it readily reduced to the latter?

As already pointed out, the notion of stability needs to be defined much more accurately. The fact that the standard reduction potential is positive has no direct bearing on the gas-phase stabilities ...
orthocresol's user avatar
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12 votes
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Can aqua regia/royal water be produced with sources of chloride and nitrate other than hydrochloric acid and nitric acid?

Not even zinc would react with neutral nitrate + chloride, why should gold ? Aqua regia must be strongly acidic for nitrates to have oxidative properties for oxidation of chlorides to chlorine and ...
Poutnik's user avatar
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11 votes
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Molecular orbital diagram of a complex including an oxido ligand

Although chemists and chemistry students alike often indiscriminatorily use the $\mathrm{t_{2g}}$ and $\mathrm{e_g}$ descriptors for the d-orbitals of a d-block metal in coordination complexes, those ...
Jan's user avatar
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11 votes

Why is tetraamminecopper(II) a square planar and not a tetrahedral species?

The short answer is that $\ce{[Cu(NH3)4]^2+}$ does not exist; the compound you are observing is $\ce{[Cu(NH3)4(H2O)2]^2+}$. It is not square planar but a Jahn-Teller distorted octahedron. You can ...
Jan's user avatar
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11 votes
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Is pyrite (FeS₂) an ionic or a covalent compound?

You seem to have fallen into the trap of thinking that ionic and covalent bonds are fundamentally different. They are not - they are just two ends of a spectrum, which has an arbitrary division ...
bon's user avatar
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11 votes

Hybridisation of Mn in potassium permanganate

I feel a bit like a broken record: Do not use hybridisation to describe coordination compounds; it is not helpful. However, the case of permanganate stands out as something where hybridisation is ...
Jan's user avatar
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11 votes

Why is manganese(II) coloured although the transition should be spin-forbidden?

To continue with the answer from @orthocresol. The breaking of formally ‘ forbidden’ transitions is very common indeed, possibly the best example is in the observation of phosphorescence from almost ...
porphyrin's user avatar
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11 votes
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Does a certain "Badecker reaction" actually exist?

The reaction in question is actually called the Boedeker reaction. How the book came from Boedeker to Badeker I do not know, but maybe there was one instance of Boedeker being written Bödeker which ...
Jan's user avatar
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11 votes
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Are complex ions thermochromic?

Indeed, this effect is observed in certain select cases. The effect of spin-spin cross over has been mentioned in this regard. There can be some other effects at play, namely: phase transitions, ...
getafix's user avatar
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