Questions tagged [quantum-chemistry]

Quantum chemistry is a subfield of quantum mechanics. Like its parent field, quantum chemistry focuses on understanding physical phenomena occuring at the atomic scale. Quantum chemistry however is more focused on providing useful descriptions of electronic structure to aid in understanding chemical problems (e.g. reactions, spectra, dynamics, ...).

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How is it that the Inner Periodic Table Sections (have 15 elements each) versus their f-block (with only 14 element’s electrons each)? [closed]

Given: 1. the “Lanthanide and Actinide” Inner Periodic Table Sections (each have 15 elements) versus the f-block Orbitals (which only have a capacity for 14 out of the 15 element’s electrons each) - ...
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Schrödinger wave function for 3s orbital of hydrogen atom [closed]

I am unable to understand what these terms in the wave function represent and how to solve it. For 3s orbital of hydrogen atom, the normalised wave function is $$Ψ_\mathrm{3s} = \frac{1}{81\sqrt{3π}}\...
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Chemical reaction energy barrier width [closed]

Well chemistry before the discovery of quantum world was saying:"In order for a chemical reaction to happen , reactants must have enough energy to be converted into products."I was wondering now that ...
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How to give different Basis set to different atoms in molecules using GAMESS-US [closed]

I am new to GAMESS-US, I am trying to do UHF for DyC10H10 while giving different basis set to Dy, C, H to reduce the computational cast. Until I tried with following input using manual. OUTPUT *** ...
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254 views

What happens if the electron in the lowest energy level of an atom loses its energy?

What happens if the electron in the lowest energy level of an atom loses its energy? Excited states spontaneously give of energy and transition to a lower energy state. Why can't an electron in the ...
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319 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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Is there a fixed corresponding orbital for every specific magnetic quantum number? [duplicate]

Does each value of $m$ have a fixed orbital (given the value of $l$ as well as $n$)? For example, if I know that $n = 2$, $l = 1$, and $m = -1$, which orbital ($\ce{p_x}$, $\ce{p_y}$ or $\ce{p_z}$) ...
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how electron can go towards nucleus and then go far apart from it as in p orbital?see discription

In p orbital shape is dumbbell shaped which means electron go in the shape of dumbbell means first towards nucleus then go away from it. How can be this possible because first electron is attracted ...
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100 views

From a Quantum Chemistry Point of View how can I break Bonds without Heating?

Is it possible to dissolve/break bonds using strong alternating magnetic fields at high frequency? (Perhaps from tesla coils?) Could you use resonance to cause the bond to weaken over time? If so how ...
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Help understanding the equation for Spin Energy in Zero Field

I’m working with a system that experiences spin frustration and for me this is the first time dealing with such a phenomenon. To grasp the concept, I’ve decided to go to the basics and read the ...
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2answers
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Why is the first affinity energy negative?

So, I've found a number of somewhat obscure responses to this question but I'm looking for something concrete: Why is the first affinity energy negative for most elements? I appreciate that this is ...
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146 views

if the shared electrons in covalent bond revolves around their nucleus, how they hold the two molecules together? [duplicate]

Covalent bonds are formed by sharing electrons. The pictures depicting this bond make it seem like that the shared electrons stay in a fixed/limited place. What happens in reality? If they rotate ...
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635 views

what is meant by stability and potential energy of molecules in cases of formation of bonds?

molecules form chemical bonds in order to gain stability. it is said that forming bonds leads to lower potential energy of molecules and makes them stable. what does stability mean? how formation of ...
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What is the magnetic quantum number -1 vs +1?

In my book it states the magnetic quantum number “$m_\ell$" is the spatial orientation of the orbital with respect to a standard set of coordinates. I get what $n$ and $\ell$ is, but what does it mean ...
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Electron tunneling between orbitals

Electrons can move through potential barriers by tunneling. Atomic/molecular orbitals are separated by energy differences. Therefore I was wondering if an electron can tunnel from one orbital to ...
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2answers
132 views

Are the electrons in an atom always 'locked' with their proton?

Suppose you have a single atom, say carbon, carbon has six electrons, and six protons. Now is there anything associating the six protons locking the six electrons other than coulombic forces? When we ...
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1answer
65 views

What is the physical significance of the fact that spin operators do not commute? [closed]

So we looked at the Stern-Gerlach experiment and I understand the basic principle; when a stream of silver atoms is passed through an inhomogeneous magnetic field, and the Ag atoms are deflected ...
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182 views

Creating Pi Molecular Orbitals from P Atomic Orbitals

As shown in the image, we have two free p orbitals in ethene but we need two p orbitals each for the bonding and anti-bonding orbital. That is a total of four. What is the concept behind this?
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3answers
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Particle-wave duality for atoms [closed]

Hmm Hello . I was wondering if we could apply the particle-wave duality of a subatomic particle for an entire atom.I know that atom is better described as space but could we apply the de Broglie ...
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Why can’t every element emit all the colours from the emission spectrum [closed]

If there is an infinite number of levels, this means that every electron can jump from as many variations as possible. Hence, why can’t every element emit every colour? Please don’t use very ...
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why molecules gain energy when heated?

molecules in solid or liquid or gas gain kinetic energy when heated. why is it like this? I request explanation in details please
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326 views

Radial expectation value for particle in a cubic box [closed]

A hydrogen atom is in a cubic box with side lengths equal to $\require{mediawiki-texvc}\pu{100 \AA{}}$. For what value of $n$ (principal quantum number) will the expectation value of the radius be ...
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245 views

Do all single-electron species have the same orbital energies? [closed]

This picture from Ebbing's General Chemistry [1, p. 234] shows the electron orbital energies for a hydrogen atom, where each subshell belonging to the same principal quantum number ($n = 1, 2, \cdots$)...
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Structure of atom [closed]

Consider one He+ ion in exited state(n=5).In the answer it is given that no. of spectral lines produced is 4 not 10.can't we use the general equation?
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Uncertainty Theorem [duplicate]

What is the physical meaning of Heisenberg's Uncertainty Principle? We have derived it mathematically but what is the logical explanation for it?
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887 views

Why the intensity vs. frequency graph initially increases for black-body radiation?

Max Planck had said that $E = n h \nu$ in his quantum theory. Then according to it, as the frequency of the light emitted increases, so the light's intensity should decrease. But it is not in the ...
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135 views

Chemical Anti-bonding and Pauli repulsion [closed]

We can explain chemical anti-bonding just using the Pauli repulsion correct?Let's take He2. 2 atoms of He share 4 1s electrons and since the magnetic spin for electrons has 2 values there would be 2 ...
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1answer
201 views

Electron Energy Levels? [closed]

New to chemistry; In my book it talks about electrons in atoms moving from one energy level or shell to another and denotes this by n. How does this exactly happen, do electrons move to different ...
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How can an atom have 2 outer shells?

For example, my textbooks says how many electrons in the outer shell in Nickel? and it says the answer is the electrons in both the d shell and s shell. Doesn't shell equal= n quantum number? And n=4 ...
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A question on spin of an electron [closed]

Can an electron have zero spin? In para hydrogen, since the nuclei have opposite spins, the they add up to 0. So is it true that one electron can have zero spin?
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Behavior of ionic salts in solution

The electrons of an isolated sodium chloride bound pair in vacuum reside at a semi-classical level in their ground state, so that the Born-Oppenheimer approximation applies, and the 'molecule' acts ...
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Identical particles: Why is triplet oxygen more stable than singlet oxygen?

Quoting from Eisberg Resnick Quantum Physics: If we consider space variables of two electrons (identical particles) to have almost the same values, then their wavefunctions are 'almost' identical ...
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How does a body lose electrons? [closed]

If there is a Na and cl in solid form , There will be atoms inside of them.How do they lose electrons ?.We know solid body has a structure and covering.Just like you can touch is the covering of table ...
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Why in Hamiltonian for hydrogen atom we have $\nabla_e$ and $\nabla_N$ and one does not operates on other? [closed]

Laplacian is $$\frac{\partial ^2}{\partial x^2}+\frac{\partial ^2}{\partial y^2}+\frac{\partial ^2}{\partial z^2} $$ Then why in Hamiltonian for hydrogen atom we have $\nabla_e^2$ and $\nabla_N^2$ and ...
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1answer
133 views

Which of the following would be an example of something that is quantized? [closed]

How do we defind quantized there, why it is climbing a flight of stairs? Thank you!
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Do higher orbitals have more energy or less energy? [duplicate]

I've recently learned that as an orbital gets larger, its energy gets closer to 0. Before this, I learned that when an electron moves down an orbital it releases the energy difference between those ...
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I'm confused please someone solve my question about electrons behavior [closed]

Where Do Electrons Get Energy to Spin Around an Atom's Nucleus? And from where that energy came from?
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What is the purpose of the equation [closed]

In my chemistry class we solved the equation wavelength = h/mv for finding the mass of a baseball and were given all of the other variables. I know that this equation has to do with wavelength of ...
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1answer
112 views

Reaction of HF in water [closed]

I was wondering, if we put $\ce{HF}$ into a glass of water the acid will be dissolved according to this reaction: $$\ce{HF->F- + H+}$$ Now there is a proton travelling across the water. All $\ce{...
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Wave-particle duality [closed]

Can I get an answer stating some analogies on how electrons behave like a wave, and what does it even mean for an electron to behave like a wave? Also, if going around the nucleus, is electron a real ...

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