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110 votes
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Do electrons really perform instantaneous quantum leaps?

Do electrons change orbitals as per QM instantaneously? In every reasonable interpretation of this question, the answer is no. But there are historical and sociological reasons why a lot of people ...
knzhou's user avatar
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65 votes
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If free electrons have classical trajectories, then why don't bound electrons around the nuclei have it too?

This is the subject of an underrated classic paper from the early days of quantum mechanics: Mott, 1929: The wave mechanics of alpha-ray tracks. Mott's introduction is better than my attempt to ...
rob's user avatar
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53 votes
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Can you please show me a final atomic model which demonstrates movement of electrons inside it?

Electrons do not move inside atoms. If an electron is in a given energy level $E$, the wavefunction is given by $\psi(x,y) = \phi(x)_{n\ell m} \,\mathrm{e}^{-\mathrm{i}E t/\hbar}$. The time ...
SuperCiocia's user avatar
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48 votes

What happens to an electron if given quantized energy to jump to a full orbital?

Overview Transitions to other unoccupied states are possible but extremely unlikely, more likely that the photon will not be absorbed. Introduction The Pauli exclusion principle prevents a third ...
Chris Long's user avatar
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47 votes
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What is a standing wave?

An animation is worth a million words:
Ruslan's user avatar
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43 votes
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Where are the inaccuracies in the Bohr model of the atom?

In hydrogen: It incorrectly predicts the number of states with given energy. This number can be seen through Zeeman splitting. In particular, it doesn't have the right angular momentum quantum ...
ZeroTheHero's user avatar
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42 votes

What do atomic orbitals represent in quantum mechanics?

(Disclaimer: I am only a highschool student and have learned the following mostly on my own. If there are any mistakes, please feel free to correct me!) An atomic orbital represents the probability ...
jng224's user avatar
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42 votes
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Why isn't the molecule of water linear straight?

There are six electrons in the outer orbital of an oxygen atom. In a water molecule two of these electrons bond with the lone electron of each hydrogen atom to form two “bond pairs”. The remaining ...
gandalf61's user avatar
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38 votes
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Why does transition from one electron shell to another shell always produce massless photon?

There are a few reasons why the particle produced needs to be a photon. Aside from conserving energy, we also need to conserve momentum, charge and spin, for example. So you would need to ask what ...
Marco Ocram's user avatar
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38 votes
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Why do "relativistic effects" come into play, when dealing with superheavy atoms?

When quantum mechanics was initially being developed, it was done so without taking into account Einstein's special theory of relativity. This meant that the chemical properties of elements were ...
joseph h's user avatar
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33 votes
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Is there actually a 0 probability of finding an electron in an orbital node?

The probability of finding the electron in some volume $V$ is given by: $$ P = \int_V \psi^*\psi\,dV \tag{1} $$ That is we construct the function called the probability density: $$ F(\mathbf x, t) =...
John Rennie's user avatar
32 votes

Why do non-hydrogen atomic orbitals have the same degeneracy structure as hydrogen orbitals?

Polyelectronic atoms don't have atomic orbitals - though they are a very useful approximation for describing the properties of polyelectronic atoms. The 1s, 2s, etc orbitals are solutions for a ...
John Rennie's user avatar
32 votes

Given that the atomic orbitals are fuzzy, why are the energy levels and energy transitions sharp?

They are "fuzzy" in position space because they have well defined energies (and therefore give rise to sharp distributions of photon energy when they change states). Foundation Quantum states (the ...
dmckee --- ex-moderator kitten's user avatar
28 votes
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Are all atoms spherically symmetric? If so, why are atoms with half-filled/filled sub-shells often quoted as 'especially' spherically symmetric?

In general, atoms need not be spherically symmetric. The source you've given is flat-out wrong. The wavefunction it mentions, $\varphi=\frac{1}{\sqrt3}[2p_x+2p_y+2p_z]$, is in no way spherically ...
Emilio Pisanty's user avatar
28 votes
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"True" quantum-mechanical description of the hydrogen atom

Summary: as for your first question - what about the motion of the proton - the answer is: after a quick transformation you get the same potential, and the mass is replaced by the "reduced mass&...
AXensen's user avatar
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27 votes

Is the probability of an electron being somewhere zero?

The Photon more or less has it right, the probability distributions of the orbitals (even in the state of being bound in an atom) extend infinitely far away radially, albeit with increasingly ...
Dion Silverman's user avatar
26 votes
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When an electron around an atom drops to a lower state, is 100% of the energy converted to a photon?

There is always energy loss due to recoil. Considering a single atom that is in free space, the total momentum is conserved, and the total reaction energy is constrained by the transition energy $E_0$ ...
Sebastian Riese's user avatar
26 votes
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What exactly is the shape of an atom as per modern physics?

The confusion arises because you have not yet learned much about quantum physics. Quantum physics is the most accurate and wide-ranging set of concepts and mathematical methods in physics, and it ...
Andrew Steane's user avatar
24 votes

Can you please show me a final atomic model which demonstrates movement of electrons inside it?

There are no final models in science, there's always room for improvement. And major paradigm shifts cannot be totally ruled out. However, we can be quite confident in our current model of the ...
PM 2Ring's user avatar
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24 votes
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Is the probability of an electron being somewhere zero?

In chapter 3, he says, if I understood this right, that electrons can only exist in specific quanta - that is they can only be in certain regions, and will perform a quantum leap over regions that are ...
The Photon's user avatar
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22 votes

Why do electrons fall from a high excitation to a lower one?

The answer is thermodynamics, and the assumption that you're working in a colder environment than the temperature corresponding to a Planck distribution where your photons would be "on average" fairly ...
entrop-x's user avatar
  • 638
22 votes

Why isn't the molecule of water linear straight?

Let's start by taking a look at the 'bare' oxygen atom. While simplistic depictions of atoms often show the electrons orbiting the nucleus on various circular orbits as if they were planets, quantum ...
Jan's user avatar
  • 328
22 votes

Do we understand chemistry from particle physics?

While the discoveries of the rules of chemistry and some current practical wisdom is empirical, it is better to think of the entire nature of chemistry as dictated by the principles of quantum ...
Matt Hanson's user avatar
  • 3,092
21 votes
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Measuring the size of the proton from the hydrogen atom spectrum?

This is an interesting and non-trivial problem. Basically the Coulomb potential assumes a point particle but, if the proton is modelled as a solid sphere of finite radius, part of the electron wave ...
ZeroTheHero's user avatar
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20 votes

Why don't all electrons contribute to total orbital angular momentum of an atom?

We describe the whole system with a state, this state is a combination of the single particle states (orbitals). Each orbital we define in terms of an orbital momentum shell. A full shell has zero ...
TEH's user avatar
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20 votes

If free electrons have classical trajectories, then why don't bound electrons around the nuclei have it too?

Free electrons do not "have" classical trajectories any more than bound ones do. How definite quantities like position and momentum are is a property of a specific quantum state, not of ...
ACuriousMind's user avatar
  • 125k
20 votes

What happens to an electron if given quantized energy to jump to a full orbital?

There are some good answers already, but I wanted to emphasize one more important point: There is actually no such a thing individual orbital energies in a multi-electron atom. So it does not even ...
Buzz's user avatar
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19 votes
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How can an electron shell hold more than two electrons?

A "shell" is the term for all states with the same principal quantum number $n$, but in each shell there are also possible different values for the angular momentum quantum number $0\leq \ell \leq n$, ...
ACuriousMind's user avatar
  • 125k
18 votes

Does substituting electrons with muons change the atomic shell configuration?

Muons, due to their higher mass, have a much smaller Bohr radius in an atom than electrons do. Muons have two spin states, just like electrons, so two muons can occupy the same orbital. A Be muonic ...
John Doty's user avatar
  • 21k
18 votes

Why do valence electrons not push each other away?

First of all, the electrons do exert a repulsive force on one another. This is inherently accounted for in the electrostatic repulsion terms in the atomic Hamiltonian that is used to solve the ...
Matt Hanson's user avatar
  • 3,092

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