Questions tagged [orbitals]

An orbital is a one-electron wavefunction, usually derived by solving the Schrodinger equation. This tag applies to questions about all forms of orbitals; additionally, questions about the construction and properties of molecular orbitals should be tagged with [molecular-orbital-theory].

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According to MO theory, why is the dilithium cation more stable than the dilithium anion?

According to molecular orbital theory, $\ce{Li2}$ fills up two electrons in the $\sigma_\mathrm{g2s}$ molecular orbital; $\ce{Li2+}$ fills up one electron in the $\sigma_\mathrm{g2s}$ MO, and $\ce{...
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Molpro - Simple explanation of OCC, CORE, FROZEN and CLOSED orbitals

I'm beginning with quantum chemistry and I'm supposed to do some ab initio calculations with Molpro. The problem is, I don't understand the orbital specification very well. Let's say, I have the ...
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Reducible representations - choice of new basis

I was looking at this tutorial about reductions of representations. At first, the basis consists of four orbitals $(s_N, s_1, s_2, s_3)$ and the representations look like this and we want to reduce ...
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288 views

What is the difference between carbon in an excited state and with sp³ hybridization?

What is the difference between the carbon in the excited state, $\ce{[(1s)^2] (2s)^1 (2p)^3}$, and $\pu{sp^3}$ hybridization?
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If a single electron fills a degenerate energy level, does it fill all degenerate orbitals at once?

For example, if a single electron fills the 2p orbitals. Since all orbitals are degenerate, there is no reason why there would be any preference for px, py, pz. Is the electron hence in a ...
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2answers
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The molecular orbitals of lithium hydride

So my understanding of molecular orbitals is as follows: the molecular orbitals of $\ce{LiH}$ can be thought of as being formed from the interaction/overlap of two atomic orbitals, one from lithium ...
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1answer
2k views

What are the magnetic quantum numbers for specific d orbitals? [closed]

I mean I know they’re $\ce{d_{-2}}$, $\ce{d_{-1}}$, $\ce{d_{0}}$, $\ce{d_{1}}$, $\ce{d_{2}}$ but how do these numbers relate to each one of $\ce{d}$ orbitals $\ce{d_{z_2}}$, $\ce{d_{xz}}$, $\ce{d_{yz}}...
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1answer
845 views

Why do the 4f and 5d orbitals have similar energies?

I've come to know this phenomena when learning about the exceptions to the aufbau principle. But there is no explanation of why 4f and 5d have similar energies (as I've read in some websites).
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Are the 2s and 2p subshells degenerate in the He+ ion?

I know that the 2s and 2p (as well as 3s, 3p, and 3d) electron subshells are degenerate in the hydrogen atom. I was wondering if they are also degenerate in other one-electron species, such as the $\...
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How is the structure of triiodide ion (I3-) possible?

I have seen the structure of triiodide ion ($\ce{I3-}$) but I cannot understand why this structure is even possible. I have seen in my textbook that $\ce{I_3^-}$ is formed by combination of $\ce{...
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Why are 4s electrons removed before 3d electrons? [duplicate]

According to Aufbau's Principle energy of 3d orbital is greater than 4s orbital, so which filling 4s if filled beforehand 3d. Whereas while removing electrons 4s electrons are removed first. Why? I ...
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1answer
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Rule to determine the total number of elements in a period [closed]

If each orbital can take maximum of 3 electrons, then total number of elements in 2nd and 4th periods respectively are = ? I am not aware of the rule which helps to determine the total number of ...
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The CASSCF orbitals

I have two questions about the orbitals that we get after the CASSCF calculations. First, what are the CASSCF orbitals that we get from these calculations? I mean after optimization, in the CASSCF ...
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How does the Jahn-Teller distortion result in both elongation and compression?

Recently, I have been reading up on the Jahn-Teller effect and I have read articles and posts on it, such as What is the mathematical basis behind the Jahn-Teller effect?. However, many of these ...
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Can a π bond form between the py and d(x2-y2) orbitals along the x-axis?

π bond does not form due to overlap between $\ce{d_{x^2-y^2}}$ and $\ce{p_y}$ along x axis? True or false? Here is a diagram of the orbitals. This pair of orbitials should be distingished from $\...
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188 views

Valence shell expansion and sulfur

I've been searching some things regarding the ability of sulfur to accomodate negative charge and reached the conclusion that it's due to its size and its ability to expand its valence shell. I can't ...
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186 views

Importance of higher order exchange terms?

The MP2 ground state energy of a molecule or solid can be written as $$E^{(2)} = \frac{1}{2}\sum^{\text{occ.}}_{ij}\sum^{\text{virt.}}_{ab} \frac{\langle ij | ab \rangle [\langle ab|ij \rangle - \...
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1answer
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What red and blue area represent in a orbital software?

I have a software in my android device named hydrogen atom. It show orbital of hydrogen we have to set the quantum numbers and probability of finding particle. But what the blue and red colour area in ...
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Probabilities of Electrons in Orbitals [duplicate]

I've heard both of the following: An orbital is a region where there's a 90% probability of finding an electron An orbital is a region where an electron spends 90% of its time Are these essentially ...
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224 views

Quantum Mechanical Model of An Atom, Shells, Subshells [duplicate]

I've just been introduced to the quantum Mechanical Model of an Atom, so please bear with me on this one. Are Subshells and shell physical things, like do they really exist, or is it a concept only to ...
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2answers
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What is the difference between the mean radial distance and the most probable radial distance of an orbital?

I was reading JD Lee's Concise Inorganic Chemistry and it has given some values of mean radial distance which is increasing from s to p to d orbital. I had earlier read that the most probable radial ...
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566 views

Why does s-p orbital separation increase with increasing atomic number? [duplicate]

More specifically, why does s-p energy separation increase: Across the period Down a group I do know that penetration of electrons increase with lower angular momentum and lower principal quantum ...
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1answer
171 views

Are there bonds which share single electron?

Are there bonds which share single electron? During chemical bonding, I asked our teacher why there are only 2 electrons shared in a bond. He said that because it's that one orbital can accommodate ...
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1answer
569 views

Volume of orbitals

As I was learning about atomic structure, the lecturer made a seemingly dubious claim: The volume of a p orbital is one-third that of the s orbital. Thus, inter-electronic repulsions are ...
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Why does a neutral atom of beryllium not have any electrons in a p orbital?

Here's what I understand about quantum number and orbitals, please correct me if anything is wrong: Electrons enter into these different types of orbitals because they have a higher/lower amount of ...
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Are all degenerate d-orbitals identical?

This discussion spun off from the comments to another question. The basic idea of that question was that electrons don't have a preferred order of filling in $p$ orbitals, i.e. the first electron will ...
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2answers
138 views

Can carbon be the central atom of a complex? Can it form a quadruple bond with itself? [closed]

Why does $\ce{[C(NH3)2]}$ not exist as a complex? Here, $\ce{C}$ is carbon and the configuration of $\ce{C}$ in ground state is $\ce{[He] 2s^2 2p^2}$. Can't the two $\ce{NH3}$ molecules pair the two ...
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592 views

Why is Cr+ unstable?

We know that half-filled and fully filled orbitals are highly stable. In ground state $\ce{Cr}$ has a $\ce{3d^5\! 4s^1}$ configuration. Therefore, the elctronic configuration of $\ce{Cr+}$ should have ...
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1answer
487 views

Which orbital lobes are occupied?

In the p-orbitals, there are 3 dumbbell-shaped lobes, each of which can contain 2 electrons. In the diagrams of the d- and f-orbitals, there are two or more lobes (or orbital shapes) or each value of ...
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1answer
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“Sea of Electrons” - do the individual electron shells interact with each other?

I've often heard metals as having a "sea of electrons". I was wondering how the actual relationships between the electron shells of individual atoms are... do the electrons orbitals overlap the same ...
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Trend in the infrared stretching of molecular hydrogen to group 8 transitions metals?

While going through old notes, in relation to the Dewar-Chatt-Duncanson model, it states that the stretching frequency for $\ce{N2}$ to the group 8 transition metals ($\nu(\ce{NN})$) proceeds as: \...
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1answer
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Why is the difference between atomic radii of Na and K greater than that of Rb and Cs?

I am aware that this question has already been asked here: Why does the "gap" between atomic radii get smaller down the periodic table?. However, I was wondering if there is a way to ...
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1answer
357 views

How to form 6-31G basis set; specific instructions

I'm new to basis sets. I read that for 3-21G, given the following basis set for carbon (from Basis Set Exchange): ...
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2answers
2k views

What is wrong with the Aufbau principle that results in so many exceptions?

From what I have observed in the periodic table is that many transition elements do not follow the Aufbau principle. And it's not just the elements like $\ce{Cu}$ and $\ce{Cr}$ that differ from ...
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2answers
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Is it correct to talk about an empty orbital?

Professor A. J. Kirby mentions: 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 ...
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1answer
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Do 1s & 2s orbitals overlap of different atoms while forming sigma bond? I

Do 1s & 2s orbitals overlap of different atoms while forming sigma bond? I think they should overlap as there will not be enough energy difference between them.
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How to derive Pauli Exclusion Principle without assuming anti-symmetry?

So, it appears that the statement of the Pauli Exclusion Principle is equivalent to the statement that fermions are anti-symmetric. That is, if you assume that fermions are anti-symmetric, then you ...
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1answer
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Where is the probability of finding an electron in 1s orbital maximum? [duplicate]

So the way I understand the question is that it asks us at what r (distance from nucleus) and at what angles is the probability going to be maximum. The way I see probability of finding at a point in ...
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1answer
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Group 15 Ionisation Energies

I had a little confusion regarding ionisation energies. I get that in general, the second ionisation energy > first ionisation energy, due to increased effective nuclear charge on the second electron....
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1answer
532 views

Phases of Atomic or Molecular Orbitals

What does phase mean in orbitals? I know that phases are separated by nodes. They are in some way related to wavefunctions, I can't understand, how? How can wavefunctions be negative, since they are ...
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1answer
63 views

What is the name of the diagram in this question? How do you read it?

My teacher calls it an 'orbital diagram' but every time I search for information something completely different pops up. I assumed it was a fancy Bohr diagram, but the electron placement is always ...
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1answer
716 views

How do you count sp3 hybridized configuration electrons for methane?

I've been reviewing my organic chemistry and upon reviewing sp3 hybridization have become confused. For methane CH4, the electron clouds rearrange into sp3 hybridization configurations of 1s2 2sp3 ...
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1answer
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Orbital diagram in which the Aufbau principle is violated [closed]

The orbital diagram in which the Aufbau principle is violated is: The answer given for this question is 3, but according to me if asked for Hund's rule violation then it would be 1, as electrons ...
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1answer
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Why does Bi show inert pair effect and not Sb?

The 6s orbital electron pair is strongly attracted by the nucleus due to the poor shielding effect of 4f and 5d orbitals. However there are other filled orbitals that shield the nucleus. In case of 5s ...
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1answer
380 views

Are electrons in a helium atom diametrically opposite? [closed]

The helium atom is represented with electron opposite on same orbital: not fully opposite on same orbital and even on two normal orbitals: But in this case wouldn't the electron crash? Can you ...
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677 views

Is Effective Nuclear Charge the same as Core Electrons?

I'm wondering, what is the difference between the two? Using the equation for Eff: $\ce{Zeff = Z - S}$ Z being the number of protons in the nucleus and S being inner-shell electrons. For example: ...
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855 views

atomic orbital probability graph for p and s orbitals [duplicate]

In the probability density graphs of s and p and even other orbitals start from nucleus as shown in the picture given below they all start from nucleus i.e. there is good probability of electrons of ...
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2answers
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Platinum Orbitals in Cisplatin Forming Bonds with LCAOs of Chlorine

My inorganic chemistry professor placed two questions on the exam review that he did not cover in class; I haven't been able to figure out how to answer them and could really use some help in learning ...
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2answers
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Why do n AOs only form n MOs? [duplicate]

The textbooks I have read introduce LCAO by considering the H2 molecule. In this example, there are only two possible combinations of the two 1s orbitals (in phase and out of phase). When there are ...
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1answer
421 views

How does the state of iodine affect its HOMO–LUMO gap?

My teacher told me that the HOMO–LUMO gap in solid iodine is smaller than that in gaseous iodine. When I asked about the reason, he told me that it is due to higher interactions in solid iodine as ...

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