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 ...
- 43.8k
21
votes
Accepted
Why do diamond and graphite have different structures, when they are both composed of carbon?
Chemical structures are a tradeoff of several factors, including the conditions on how they were formed.
The stability of any given chemical structure depends on the ease with which any specific ...
- 35.5k
19
votes
Accepted
Why do XeO and XeF8 not exist?
$\ce{XeF8}$ is not known to exist though O.N is +8. Why is this so?
At least 2 compounds have been reported that contain the $\ce{XeF8^{2-}}$ unit. See, for example:
$\ce{(NO^+)2[XeF8]^{2-}}$ (...
- 84.2k
19
votes
Accepted
How can FeS2 be the formula of iron sulphide and CaC2 be the formula of calcium carbide?
What you call iron sulphide, in my opinion, is more appropriately referred to as or iron disulphide.
If one were to assign oxidation states to each atom, an appropriate description would be $\ce{Fe^...
- 8,465
18
votes
Accepted
Do Li4 or Li8 molecules exist?
Yes, they do exist and were characterised spectroscopically, see here (and there is a note on similar clusters for sodium):
Blanc, J.; Bonačić‐Koutecký, V.; Broyer, M.; Chevaleyre, J.; Dugourd, P.; ...
- 21.5k
15
votes
Accepted
Effect of noble gas configuration on polarising power
Recall the fact that the basic difference between an ionic bond and a covalent bond, is basically just charge separation. In ionic bonds, charges are well separated, and the bond arises due to ...
14
votes
Is potassium bifluoride an ionic or a covalent compound?
Yes, $\ce{KHF2}$ is an ionic compound and a covalent compound. There is nothing exceptional about it; in fact, most compounds that we call ionic (not $\ce{NaCl}$, though) have covalent bonds in them. ...
- 31.1k
13
votes
Accepted
Is potassium bifluoride an ionic or a covalent compound?
I found this question very intriguing and while I support both answers by Ivan and Mithoron, I would like to add a little more insight.
When we consider compounds, we often tend to describe them as ...
- 43.8k
13
votes
Covalent and Ionic Bonds
Bonds are usually used to describe how electrons are shared. "Partially ionic bonds" are polar covalent bonds. Which is not the same as saying that a compound has different types of bonds in the whole ...
- 4,284
12
votes
How can FeS2 be the formula of iron sulphide and CaC2 be the formula of calcium carbide?
There is no point in doubting the composition of these compounds, the measurements don't lie. ;-)
The point is that S or C (or e.g. P) can not only form bonds to the metal, but also between ...
- 12k
11
votes
Why the bond angle of PH3 is lesser that that of PF3?
VSEPR works by accident in the cases of $\ce{NH3}$ and $\ce{NF3}$. In reality, there are much more things to consider as shown in this answer. All four compounds should have bond angles of $90^\circ$ ...
- 67.3k
11
votes
Accepted
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 ...
- 15.3k
11
votes
Is potassium bifluoride an ionic or a covalent compound?
$\ce{KHF2}$ is an ionic compound with cation $\ce{K+}$ and anion $\ce{HF2-}$, and writing $\ce{KF.HF}$ doesn't suggest covalent bond between K and F, but say that $\ce{HF2-}$ anion is adduct of F- ...
- 4,576
11
votes
Accepted
Is beryllium difluoride covalent or ionic?
There is a very relevant article by Gillespie Covalent and Ionic Molecules: Why Are BeF2 and AlF3 High Melting Point Solids whereas BF3 and SiF4 Are Gases? J. Chem. Educ., 1998, 75 (7), p 923.
...
- 40.3k
11
votes
Accepted
How are the π bonds arranged in Osmium Tetroxide?
Your conception of $\pi$-bonds is a bit too restrictive. A $\pi$-bond is a bond in which there is one node along the internuclear axis. So, yes, two side-on $p$-orbitals do form a $\pi$ bond because ...
- 3,060
10
votes
Why do XeO and XeF8 not exist?
According to Heats of Formation of XeF3+, XeF3-, XeF5+, XeF7+, XeF7-, and XeF8 from High Level Electronic Structure Calculations Inorganic Chemistry 2010, vol. 49, pages 261–270:
Unlike
the ...
- 40.3k
10
votes
Accepted
Do both electrons in a dative bond come from the same atom?
Your textbook’s definition is inconsistent for exactly the reasons you point out. I am going to use slightly different examples than you did but they work equally well.
A prime example for dative ...
- 67.3k
10
votes
Accepted
Is a hydrogen molecule smaller than hydrogen atom?
You can define the size of atoms and molecules in various ways. You can, for instance, derive a measure of the size of a hydrogen molecule from the density of solid hydrogen:
Solid hydrogen has a ...
- 20.9k
10
votes
Does lithium form ionic hydride?
As described in the comments, there really is no sharp boundary between "ionic" and "covalent" bonding. With metal hydrides the situation is muddled further because the usual ...
- 53.4k
9
votes
Accepted
Increasing Covalent character increases Colour intensity
In molecular orbital theory, as the covalent character increases the homo-lumo gap decreases, and the excitation happens more easily. Thus the colour intensity increases.
- 106
9
votes
Will supercritical nitrogen stay supercritical if we raise temperature and pressure high above critical values?
If we maintain nitrogen at 220 bar and 400 °C, what will be the state of $\ce{N2}$? Will it be still supercritical?
Yes, it will still be supercritical. The only reasonable definition of "...
- 21.8k
9
votes
Relative O-O bond lengths in O2X2 molecules (X = H, F, Cl)
First, let me confirm your answer. The table given below shows a summary of optimised structures of $\ce{XOOX}$ compounds; experimental data when available is in parentheses. As a reference the bond ...
- 8,465
8
votes
Why do ionic compounds dissociate whereas coordinate complexes won't?
‘Ionic bonds dissociate but coordination complexes don’t’ is an oversimplification in a number of ways.
As tschoppi already mentioned, ligand exchange, i.e. complex dissociation and reassociation is ...
- 67.3k
8
votes
Why are noble metals more electronegative then most metals?
The noble metals are defined by a resistance to oxidation and corrosion, and this should not be interpreted as a lack of reactivity, but instead an aspect of their high EN. So, there is no ...
- 657
8
votes
Accepted
Which has the largest bond angle between water, oxygen difluoride and dichlorine oxide?
There is practically only one effect that determines the angle, but there is an underlying mechanism that you also should understand.
Ideally, a central atom such as oxygen would want to use its p-...
- 67.3k
8
votes
How can sulfate be nonpolar covalent if it is a polyatomic ion?
These two species have bonds within them, and (non)polar covalency refers to those internal bonds. The species as a whole can be an ion, and yet not have net polarity on its bonds.
Sulfate is ...
- 673
8
votes
Accepted
Relative O-O bond lengths in O2X2 molecules (X = H, F, Cl)
First things first: the shorter a bond, the higher the multiple bond character. I.e. a double bond is shorter than a single bond, and a bond with a bond order of $1.5$ is in the middle of the two. ...
- 67.3k
8
votes
Accepted
What is melting? Which bonds do we break to melt something?
This is a good question. Unfortunately there are several criteria by which chemists indentify whether a process is melting or not. One of them is called the Lindemann Criteria which says:
"Crystals ...
8
votes
Covalent and Ionic Bonds
If you are asked on a test "Is sodium nitrate ionic or covalent?", say "ionic" and if given the opportunity, justify your answer with electrical conductivity of molten sodium nitrate and aqueous ...
- 40.3k
8
votes
Accepted
Number of Sigma Bonds in this Structure Containing a Ring
There're are 13 sigma bonds there (count the red lines),
You've clearly tried to attempt this yourself, so good on you (and by virtue of that, it's equally clear that you counted the bonds too ...
- 18.6k
Only top scored, non community-wiki answers of a minimum length are eligible