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156 votes
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Why doesn't H₄O²⁺ exist?

I myself was always confused why $\ce{H3O^+}$ is so well-known and yet almost nobody talks of $\ce{H4O^2+}$. I mean, $\ce{H3O^+}$ still has a lone pair, right? Why can't another proton just latch onto ...
Nicolau Saker Neto's user avatar
32 votes
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Does the term 'Cation' always refer to a positively charged particle?

Yes, cations always have a positive charge and anions always have a negative one. The difficulty is that the term cathode and anode do not always correspond to the same pole. The cathode is that pole ...
Jan's user avatar
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24 votes

Do non-classical carbanions exist?

Interesting question. It is much less studied and reported on than the case of non-classical carbocations, but I did find a few papers. Brown and Occolowitz (Ref.1) reported that deuterated bicyclo[3....
Organic Chemistry Explained's user avatar
22 votes

How was it concluded that the H3O+ rather than H+ is the "acid" ion?

Actually, the initial theories before Lewis suggested that $\ce{H+}$ is the cause of acidity. However, it soon turned up that an ion as small as the nucleus of hydrogen (you may simply call it a ...
N Shultz's user avatar
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22 votes
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Why are protons more common than hydride ion?

This is because we live in a world dominated by oxygen and water. In other words, it is an oxidized world. Most metals occur naturally in the form of oxides, silicates, halides, or other derivatives. ...
Ivan Neretin's user avatar
19 votes

Why doesn't H₄O²⁺ exist?

In chemistry ask "why" only after you ask "if". Given a sufficiently strong superacidic medium, $\ce{H3O^+}$ can be protonated to $\ce{H4O^{2+}}$. Evidence for this reaction, by ...
Oscar Lanzi's user avatar
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18 votes
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Do non-classical carbanions exist?

In addition to the species mentioned in the answer above, I found another one in Organic Chemistry by Morrison and Boyd(Seventh Edition)
Yusuf Hasan's user avatar
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18 votes

Can glass be deionized?

You can indeed "harden" glass by exchanging ions on the surface, but not because it turns into quartz glass. Quartz glass is mostly so robust because it has an extremely small thermal expansion ...
Karl's user avatar
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17 votes
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Can H4O 2+ form?

The existence of $\ce{H4O^{2+}}$ has been inferred from hydrogen/deuterium isotopic exchange monitored through $\ce{^{17}O}$ NMR spectroscopy in the most extremely acidic condensed phase superacid we ...
Nicolau Saker Neto's user avatar
17 votes
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Why are bromine oxyanions uncommon?

I can only really speak for bromine(VII). Bromine(V) is pretty common and I'm not entirely sure what's the deal with Br(I) readily disproportionating to Br(V) + Br(-1). (The tendency of Br(I) to ...
orthocresol's user avatar
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17 votes

Does the term 'Cation' always refer to a positively charged particle?

From what I was taught in Middle-school, cations are those ions that move towards the cathode, likewise anions are those ions which move towards the anode. Nope, the definitions are as follows (from ...
Wildcat's user avatar
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16 votes
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Does the hydrogen ion actually exist?

Yes free $\ce{H+}$ ions, protons, really exist. Protons are constantly emanating from the sun and reaching Earth. The proton flux is continuously monitored by satellite. However, in a ...
DavePhD's user avatar
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15 votes
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Superscript and subscript together after the same atom

From IUPAC Green Book [1, p. 51]: In writing the formula for a complex ion, spacing for charge number can be added (staggered arrangement), as well as parentheses: $\ce{SO4^2-}$, $\ce{(SO4)^2-}$. The ...
andselisk's user avatar
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14 votes
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Why does the same electron transition release photons of different frequencies for some elements?

I am glad that you updated the question because it highlights a very common misconception. First of all the JavaLab Flame Test is completely wrong for both copper, calcium and many more salts ...
AChem's user avatar
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13 votes

Why is the magnesium(II) ion preferred over other ions in chlorophyll?

Chlorophyll in plants has two main functions. First, it facilitates energy transfer of an absorbed photon's energy via the many other chlorophylls that constitute the antenna pigment-protein complex ...
porphyrin's user avatar
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13 votes

Origin of Azide's Name

Nitrogen was originally called 'azote' by Lavoisier. This name persists in many nitrogen containing species such as azide, hydrazine, diazonium etc. The '-ide' ending is the standard ending for ...
bon's user avatar
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13 votes

Origin of Azide's Name

Bon explains in their answer that Nitrogen was originally called 'azote' by Lavoisier. And it was called 'azote' because living things cannot survive in the gas. From Greek a- "not, without" [.....
Au101's user avatar
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13 votes

Why doesn't H₄O²⁺ exist?

$\ce{H4O^{2+}}$ would be much smaller than $\ce{SO4^2-}$. The charge density is too high much higher. The oxygen in water already becomes electron-deficient when it forms $\ce{H3O+}$. In your (not ...
Karl's user avatar
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13 votes
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Do quaternary sulfur dications exist?

Ogawa et al. [1] were first to report a crystal structure (CSD-YAFNOI) of a compound with quaternary sulfur, bis(2,2′-biphenylylene)sulfurane: Figure 1. Molecular structure of bis(2,2'-biphenylene)...
andselisk's user avatar
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13 votes

Is there a material that ions can pass through but water can’t?

There are so many materials that allow the passage of ions but not water. They are called ion-exchange membranes. I believe you are interested in water purification based on your previous posts. The ...
AChem's user avatar
  • 39.1k
12 votes

Do ligands with a positive charge exist?

In addition to already mentioned cationic onium ligands, there is hydrazinium $\ce{H2N-NH3+}$ and its derivatives [1 -- 3]. Crystal structure of hydrazinium-trichloro-copper(II) $\ce{Cu(N2H5)Cl3}$ [...
andselisk's user avatar
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11 votes

Why is the magnesium(II) ion preferred over other ions in chlorophyll?

Magnesium ions tune the electronic properties of the tetrapyrole ring of chlorophyll. Why would the delicate photosythetic machinery fail if magnesium was substituted with calcium or zinc ions? My ...
julien's user avatar
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11 votes
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Is there a preferred way of naming the resonance hybrid in keto-enol tautomerism?

Nomenclature of Organic Chemistry, IUPAC Recommendations and Preferred names 2013 in the section P-76 DELOCALIZED RADICALS AND IONS mentions only "totally delocalized" ions like cyclopentadiene ...
mykhal's user avatar
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11 votes
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How does aluminium react with bases to form aluminates?

There's no positive charge on Al, yet it reacts with hydroxide groups floating around. Your observation is correct. In the beginning, aluminium in its elemental state has the oxidation state 0. ...
Klaus-Dieter Warzecha's user avatar
11 votes
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Can an ion isotope exist?

Short answer: Yes. Longer answer: Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. Everything else about them is the same. The numbers of protons and ...
Ben Norris's user avatar
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11 votes

Strongest negative inductive effect group between trimethylammonium, ammonium and dimethylsulfonium groups

The inductive effect can be quantitatively measured by the Hammett equation $$\sigma(\ce{X}) = \mathrm{p}K_\mathrm{a}(\ce{H}) - \mathrm{p}K_\mathrm{a}(\ce{X})$$ where $\mathrm{p}K_\mathrm{a}(\ce{X})$...
orthocresol's user avatar
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10 votes
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Strongest negative inductive effect group between trimethylammonium, ammonium and dimethylsulfonium groups

Methyl groups are great at stabilising carbenium ions via an inductive effect — which should actually be considered a resonance effect — known as hyperconjugation. This effect, which is actually due ...
Jan's user avatar
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10 votes
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What kind of 'product' is the 'product' in 'ionic product of water'?

Per Zhe's comment, in the specific context of the term ionic product of water, the word product is used in the sense of the result of the mathematical operation of multiplication: The ionic product ...
hBy2Py's user avatar
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