40 votes
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An introduction to "oxidation state"/"oxidation number"

TL;DR; Oxidation States are useful tools used in nomenclature, redox chemistry etc. There are a few simplistic rules to determine the oxidation state of elements in an atom; but they're not ...
M.A.R.'s user avatar
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26 votes
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Is it possible for one specific atom in a molecule to have a non-integer oxidation state?

It depends. Consider various radicals such as the superoxide anion $\ce{O2^{.-}}$ or $\ce{NO2^{.}}$. For both of these, we can draw simple Lewis representations: In these structures, the oxygen atoms ...
Jan'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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23 votes

Does fluorine in FNO3 have +1 oxidation number?

tl;dr The ambiguity is due to an unfortunate incompleteness of the previously (prior to 2016) existing rules. The oxidation state of fluorine in $\ce{FNO3}$ is $-1$ according to the present rules. As ...
Martin - マーチン's user avatar
23 votes
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Can fluorine ever have a positive oxidation state?

As noted in the referenced question, fluorine is not in the +1 oxidation state in hypofluorous acid (which, incidentally, is the only hypohalous acid that has been isolated) nor in any other compound ...
Oscar Lanzi's user avatar
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17 votes
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Can osmium react with oxygen at room temperature?

From Encylopedia Britannica: Of the platinum metals, osmium is the most rapidly attacked by air. The powdered metal, even at room temperature, exudes the characteristic odour of the poisonous, ...
Waylander's user avatar
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16 votes

Why isn't thallium triiodide stable?

Thallium triiodide does exist and it is formulated as $\ce{Tl+I3-}$ and not $\ce{Tl^3+(I^{-})3}$. Thus $\ce{TlI3}$ is a thallium(I) compound and contains the triiodide ion, $\ce{I3^{−}}$. This is ...
Nilay Ghosh's user avatar
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16 votes
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How does potassium hexfluoronickelate(IV) exist in a stable state?

To quote from the comments: you can get things into an amazing variety of oxidation state given the right environment. In the case of maximal oxidation states, particularly above $+2$ or $+3$ in the $...
Oscar Lanzi's user avatar
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14 votes

Oxidation state of fluorine in HOF

There is no anomaly in here. Fluorine’s oxidation state in $\ce{HOF}$ is $\mathrm{-I}$ as the theory says. Hydrogen’s is $\mathrm{+I}$. This leaves oxygen with an oxidation state of $\mathrm{\pm 0}$. ...
Jan'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
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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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12 votes

Is it possible for one specific atom in a molecule to have a non-integer oxidation state?

IUPAC recognizes that there are fractional oxidation states, but asks that you avoid writing them. IR 4.6.1 says not to write an oxidation state "where it is not feasible or reasonable to define&...
DavePhD's user avatar
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12 votes
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Is it possible for halogens to show oxidation states less than -1?

Yes, they can show oxidation states lower than -1. For example in hyperlithiated compounds, like $\ce{Li3Cl}$, the chlorine would formally have an oxidation state of -3. However, a word of caution, ...
Philipp's user avatar
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11 votes
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Oxidation state of nitrogen in HN3

This answer uses electronegativities for the calculation of oxidation states as proposed in the Expanded Definition of the Oxidation State by Hans-Peter Loock in 2011. Comparing Electronegativities ...
lcnittl's user avatar
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11 votes
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What is the oxidation state of copper and iron in chalcopyrite?

A number of papers report that the formal valency states of chalcopyrite are best considered as $\ce{Cu+Fe^3+S2}$, based on various computational and spectroscopic evidence. References: Klekovkina, ...
bon's user avatar
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11 votes

What are oxidation states used for?

Of course they are useful. Perhaps you have not come across them yet, but being able to determine the oxidation state of an atom allows us to understand the properties of chemicals and how redox ...
orthocresol's user avatar
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11 votes
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What is the n factor of H2O2 undergoing disproportionation reaction liberating oxygen

I want to elaborate the answer of Ashish Ahuja because he is also perplexed by the n-factors. First of all for general readers n-factors are of historical interest only. Due to my interest in ...
AChem's user avatar
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11 votes

Can osmium react with oxygen at room temperature?

As the others already stated, handling pure Osmium is too dangerous at home, but there are shops that offer small samples of elements sealed in acrylic glass, which is supposed to be safe. Maybe this ...
Eldrad's user avatar
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10 votes
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What is the oxidation state of nitrogen in N2O5?

It is +5 .Even by the structure. Notice that it is a resonance structure of: Now one of the bonds are coordinate bonds where nitrogen donates BOTH its electrons to oxygen (otherwise, oxygen cannot ...
Varun's user avatar
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10 votes
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Why doesn't iron(III) iodide exist?

The standard reduction potentials for the following half reactions can be found here. $$ \begin{align} \ce{Fe^3+(aq) + e- &-> Fe^2+(aq)} &\quad E^\circ &= \pu{+0.77 V} \\ \ce{I2(s) + 2 ...
bon's user avatar
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10 votes
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Oxidation state of fluorine in HOF

While I agree with the outcome of Jan's assignment of oxidation numbers, it is very necessary to point out that this is not the only possible assignment, (probably still) not even the most common one. ...
Martin - マーチン's user avatar
10 votes
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Oxidation states of oxygen

The concept of oxidation state simply works on concept of electronegativity.The more electronegative atom acquire a negative charge while less electronegative atom acquire a positive charge. Depending ...
Vidyanshu Mishra's user avatar
10 votes

What are oxidation states used for?

I would say the main relevance of oxidation states is qualitative, not quantitative. Sure enough, it is possible to give a detailed quantitative picture of redox reactions in terms of quantum ...
duplode's user avatar
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10 votes
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What is the nature of the Fe–O2 binding in oxymyoglobin and oxyhemoglobin?

TL;DR: It is not really "one or the other" - it is more of "somewhere in between", like a resonance hybrid. If I had to choose, I'd personally lean towards Weiss's $\ce{Fe(III)-O2-}$ model. However, ...
orthocresol's user avatar
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10 votes

Can osmium react with oxygen at room temperature?

According to Wikipedia: Finely divided metallic osmium is pyrophoric[1] and reacts with oxygen at room temperature, forming volatile osmium tetroxide. Some osmium compounds are also converted to the ...
Oscar Lanzi's user avatar
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9 votes

Why oxidation number of oxygen in OF2(oxygen difluoride) is +2?

Oxygen is an electronegative element -True. But oxygen is not the most electronegative element. It has an electro negativity of 3.5 on Pauling scale. That means if oxygen combines with an element ...
Serotonin's user avatar
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8 votes

Is it possible for one specific atom in a molecule to have a non-integer oxidation state?

According to the IUPAC Gold Book[1], oxidation state is defined as: A measure of the degree of oxidation of an atom in a substance. It is defined as the charge an atom might be imagined to have ...
bon's user avatar
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8 votes
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Why don't we see these lanthanide species?

This is really the exact same question but just in a different context of transition metals: Cr(II) and Mn(III) - their oxidizing and reducing properties? The answer is because exchange energy (which ...
orthocresol's user avatar
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8 votes

The teacher insists that iodine oxidation number in iodate ion is 7

Plus 5 according to: https://en.wikipedia.org/wiki/Iodate Teachers do sometimes make mistakes.
bpedit's user avatar
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