40 votes

What are angular and radial nodes?

The accepted answer has nice pictures, but has a couple of small factual inaccuracies in the last paragraph. In particular, it is not necessary for an angular node to be a plane (even though it ...
orthocresol's user avatar
  • 70.8k
40 votes

Why are covalent bonds directional?

The meaning of covalent bonds being directional is that atoms bonded covalently prefer specific orientations in space relative to one another. As a result, molecules in which atoms are bonded ...
Wildcat's user avatar
  • 18.8k
35 votes
Accepted

How do I visualize an atom?

I have searched and searched, oh how I have searched. Do you know what I always tell my mom when she asks me to find something in the Internet she was not able to find herself? I ask her: "Are you ...
Wildcat's user avatar
  • 18.8k
32 votes

When are two orbitals orthogonal?

Unfortunately, the sense in which orbitals are orthogonal is more or less impossible to define rigorously without recourse to functions of some kind. So, I'll give an explanation a shot using some ...
hBy2Py's user avatar
  • 17.2k
27 votes
Accepted

Why is the letter J omitted in the spdf... sequence?

Omitting j when alphabetically enumerating things has a long tradition. First of all, the alphabet did not always exist in the form we know it today. Quoting Wikipedia: After [...] the 1st century ...
mhchem's user avatar
  • 3,306
27 votes

Why do n AOs only form n MOs?

If you have $n$ functions (e.g. AOs) you can make a maximum of $n$ new linearly independent functions (e.g. MOs). If you try to make $n+1$ MOs, then any one of them can be expressed as a linear ...
Jan Jensen's user avatar
  • 4,789
24 votes
Accepted

Canonical MOs vs. Localized MOs: Do both represent reality in the same way?

NOTE: In the below, I'm implicitly discussing a ground-state, closed-shell wavefunction, where all occupied orbitals are doubly occupied. The discussion would be similar for open-shell wavefunctions, ...
hBy2Py's user avatar
  • 17.2k
23 votes

Physical intuition behind negative values for wave function?

The wavefunction of a particle actually has no physical interpretation to it until an operator is applied to it such as the Hamiltonian operator, or if you square it which gives its probability of ...
Nanoputian's user avatar
  • 7,332
23 votes
Accepted

Shape of the P1/2 Orbital

As orthocresol mentioned, this is all about relativity, so let's talk about it. I am hardly an expert myself, but I'll try to give an answer to the best of my limited knowledge. For an interesting and ...
Nicolau Saker Neto's user avatar
23 votes

Why is the letter J omitted in the spdf... sequence?

For the azimuthal quantum number (l) of an atom, there is no "j" because some languages do not distinguish between the letters "i" and "j". L is the total orbital quantum number in spectroscopic ...
MaxW's user avatar
  • 22.2k
21 votes
Accepted

Degeneracy of second excited state of H-?

I think it is important to understand that for hydrogen atom (or any other one-electron system) all orbitals from the same shell have same energy. For instance, $E_\mathrm{2s} = E_\mathrm{2p}$, $E_\...
Wildcat's user avatar
  • 18.8k
20 votes
Accepted

Are the canonical orbitals of Hartree-Fock also the natural orbitals?

There is a bit of a terminology problem in the field that makes things very confusing and I will try to clarify some of this here. Part of the problem arises from the fact that sometimes only one kind ...
levineds's user avatar
  • 3,040
19 votes
Accepted

When are two orbitals orthogonal?

One atomic (or molecular) orbital is said to be orthogonal to another atomic (or molecular) orbital if there is no interaction between the electrons in one orbital with the electrons (wavefunction) in ...
ron's user avatar
  • 84k
18 votes
Accepted

How to convert from spin orbitals to spatial orbitals in the Hartree-Fock approximation?

Technical Note: This page makes heavy use of MathJax, give it time to load. $ %some shortcuts \newcommand{\op}[1]{\mathbf{#1}} \newcommand{\ve}[1]{\mathbf{#1}} \newcommand{\id}[1]{\mathrm{#1}} \...
Martin - マーチン's user avatar
18 votes
Accepted

What is Drago's rule? Does it really exist?

Going through what you posted, I think ‘Drago’s rule’ (which I never encountered, either at school or at university) gives good predictions but uses a largely terrible set of arguments. For any atomic ...
Jan's user avatar
  • 66.9k
18 votes
Accepted

Shape of a wavefunction

You are plotting different functions. The figures have no reason to be more than vaguely reminiscent of each other. Now, those nice puffy things above are the isosurfaces of $\psi$ function. This is ...
Ivan Neretin's user avatar
  • 30.9k
18 votes
Accepted

Can the idea of entropy be extended to orbitals?

No. The reason why a gas particle in a large volume has a large entropy is not because it has a lot of space to move around per se. A better explanation is that for a given energy, there are many ...
orthocresol's user avatar
  • 70.8k
18 votes
Accepted

Is the notion of orbitals different in theoretical chemistry?

Unfortunately, it only gets more complicated the deeper you dig. There is some explanation here: What exactly is an orbital?, but you should bear in mind that electronic structure theory is something ...
orthocresol's user avatar
  • 70.8k
17 votes

Simple Explanation of orbitals

Well, the first step is to stop thinking electrons as being very small balls that orbit around the nucleus in a circular path. This is known as the Bohr model. Despite this model being an excellent ...
Nanoputian's user avatar
  • 7,332
16 votes

How do I visualize an atom?

I am looking for a 3 dimensional visualization of a whole (moderately complex, hydrogen is just a ball) atom that includes 3 dimensional orbital geometry. 3 dimensions is only enough to represent the ...
DavePhD's user avatar
  • 40.1k
16 votes

Why do electrons jump back after absorbing energy and moving to a higher energy level?

This is a very fundamental question and for really understanding the "why" some advanced physics is involved. I will describe the process rather superficially. As you might know, the level ...
Paul's user avatar
  • 2,386
16 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
15 votes
Accepted

Why a higher s character increases a carbon atom's electronegativity?

Electronegativity is the power of an atom to attract bonding pairs of electrons to itself. It clearly depends on the nuclear charge: the larger it is, the more strongly the nucleus attracts electrons ...
Wildcat's user avatar
  • 18.8k
15 votes
Accepted

Is it correct to talk about an empty orbital?

"The properties of an orbital are those of an electron contained in it. It is normal practice, illogical though it may sound, to talk of 'vacant orbitals'. The properties of vacant orbitals are those ...
TAR86's user avatar
  • 6,851
14 votes
Accepted

Why is the principal quantum number irrational?

So, first, as I said in my comment, you confused the orbital angular momentum quantum number $l$ with the principal quantum number $n$. Both can take only integer values (positive and non-negative ...
Wildcat's user avatar
  • 18.8k
14 votes
Accepted

What is the hybridization of terminal fluorine atoms in molecules like boron trifluoride?

TL;DR: As a rule of thumb, terminal (heavy) atoms are almost always best described as having sp hybrid orbitals (at the most). For more on this, I refer you to my answer on What is the hybridization ...
Martin - マーチン's user avatar
14 votes
Accepted

Predicting sigma bond overlap strengths of s-s, p-p, s-p, sp-sp etc

I think the issue might be what orbitals are being referred to. Both books could be correct if they are referring to different $\mathrm{p-p}$ overlap. For example, suppose two atoms are bonding along ...
Tyberius's user avatar
  • 11.6k
14 votes
Accepted

Are all degenerate d-orbitals identical?

Yes, they are identical. One thing that we don't really teach well with orbitals is thinking about the symmetry of the orbital with respect to the name of the orbital. $p_{x}$ has the same symmetry as ...
Zhe's user avatar
  • 17.2k
14 votes
Accepted

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
  • 38.3k
13 votes

Simple Explanation of orbitals

Why don't you try with analogies: at least, as a vary basic introduction, I very much appreciate the attempt done here by Goh et al. An orbital is defined as a region in space in which there is ...
mannaia's user avatar
  • 1,738

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