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27 votes

Why does hydrogen burn with a pale blue flame while its emission spectral lines are red in colour?

It is a very interesting question, but comparing a combustion spectrum with an atomic emission one is like comparing apples and oranges. A flame is a luminous gas phase chemical reaction where the ...
ACR's user avatar
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18 votes

Do electrons have some volume, area or shape?

Quoting from the Nobel lecture of Hans G. Dehmelt (1989): With the rise of Dirac’s theory of the electron in the late twenties their size shrunk to mathematically zero. Everybody “knew” then ...
DavePhD's user avatar
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18 votes

Which atom is the smallest atom?

The volumes of the nuclei are negligible compared to the atomic radii (like a "pea in a soccer/football/cricket stadium"). The higher the nuclear charge, the closer the electrons to the ...
Karsten's user avatar
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17 votes
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Do electrons have some volume, area or shape?

Atoms are composed of a positively charged nucleus and an outer shell of negatively charged electrons. When two atoms come into close proximity, their electron shells repel, preventing the atoms from ...
Acccumulation's user avatar
16 votes

Why is it that protons and electrons undergo the same amount of deflection in an electric field if they have the same energy?

Now that's a mildly non-trivial observation. Why would they be equal, really? Let's say a particle with mass $m$, charge $q$, and initial velocity $v$ enters an area of length $L$ where an electric ...
Ivan Neretin's user avatar
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15 votes
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Excitation of hydrogen atom

[...] will it stay in the s subshell with an increasing value of n? Quite the opposite, in fact: it can't go from $\mathrm{1s} \to \mathrm{2s}$, $\mathrm{1s} \to \mathrm{3s}$, or any $\mathrm{1s} \to ...
orthocresol's user avatar
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14 votes
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How to find the orbital a given wavefunction represents?

An easier way is to search for nodes, i.e. regions where the wavefunction is zero. Clearly, the $r^2$ term means that $\psi = 0$ at $r = 0$ (i.e. the nucleus). Also, the $\exp(-kr)$ term means that $\...
orthocresol's user avatar
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13 votes
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What is the exact definition of the radial distribution function?

The atomic orbitals (wavefunctions) $\psi(r,\theta,\phi)$ are comprised of a radial component $R_{n,l}(r)$, as well as an angular component $Y_{l,m}(\theta,\phi)$. These are obtained by separately ...
orthocresol's user avatar
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12 votes
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Basics of wave-mechanical model of atom

These orbitals represent the angular part of the wavefunction. The solution obtained directly from solving the Schrödinger equation produces equations containing complex numbers so cannot be drawn on ...
porphyrin's user avatar
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11 votes

Cause of uniform glow in cathode ray tubes

The uniform glow is due to ionization and recombination of the residual gas; it's called a glow discharge. At higher pressure, a spark or arc discharge occurs at much higher current density. ...
DrMoishe Pippik's user avatar
11 votes
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Terminology of atomic spectroscopy: Difference Among Term, States and Level

The figure below shows the situation between configuration for a $p^2$ configuration, terms, levels and states. The word 'state' tends to be used colloquially to mean any of Term, Level or State. ...
porphyrin's user avatar
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11 votes

Huge variation of the atomic size of Uranium

Uranium has more valence electrons capable of populating bonding molecular orbitals (or bonding electronic bands) when compared to thorium - basically, uranium is closer to the middle of its block, ...
Nicolau Saker Neto's user avatar
10 votes

How does de Broglie actually prove Bohr's postulates?

de Brogile explains why orbitals are quantised Strictly speaking de Brogile doesn't prove Bohr's postulates which are mostly wrong. But he did provide an explanation for the most important of Bohr's ...
matt_black's user avatar
9 votes

Does electron mass decrease when it changes its orbit?

I'd like to copy the answer by John Rennie to a similar question at Physics.SE, since it's much better than current answers here IMHO. Although it mostly speaks about binding energy, the same ...
8 votes

Why can't the energy of an electron exceed 0 eV?

The value of the energy in the Bohr model is zero when the quantum number is infinity because that is the limiting value of the Coulombic potential at large distances, and because the electron is ...
Buck Thorn's user avatar
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8 votes
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Why is potassium less dense than sodium?

Although density may be a relatively easily measurable property of solid materials, it may not suggest the most fundamental relationship between mass and volume for the elements. Molar volume (the ...
James Gaidis's user avatar
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8 votes

How to find the orbital a given wavefunction represents?

The general form of the radial wave function for hydrogen like atom is, $$ R(r) = - \sqrt{ \Bigl(\frac{2Z}{na_o}\Bigr)^3 \frac{(n-l-1)!}{2n(n+l)!}}e^{-\frac{Zr}{na_o}} \Bigl(\frac{2Zr}{na_o}\Bigr)^l L$...
Infinite's user avatar
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7 votes

What happens to the first ionization potential when a hydrogen-like atom captures a particle?

When we solve the Schrodinger equation for the hydrogen atom we general make the simplifying assumption that the proton stays fixed and the electron moves in the potential of the fixed positive charge....
John Rennie's user avatar
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7 votes
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Electron pairing in atoms

The configuration for the free atoms is: Ba - $\mathrm{[Xe]\ 6s^2}$ Br - $\mathrm{[Ar]\ 3d^{10} 4s^2 4p^5}$ S - $\mathrm{[Ne]\ 3s^2 3p^4}$ Si - $\mathrm{[Ne]\ 3s^2 3p^2}$ Thus: Barium has no ...
MaxW's user avatar
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7 votes
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The true shape of p orbitals

There is a misconception here. A p orbital is a 3D-function, and these functions don't have shapes, they have values at any point in space. If you describe an electron distribution with one of these ...
Karsten's user avatar
  • 40.8k
7 votes

Is the given statement regarding Radial Probability Distribution Function correct or not?

Conceptually you are right as the commenters have mentioned, but since we are on a thread about nitpicking, we might as well go the extra distance. Technically, $r^2R^2$ itself is not a probability ...
orthocresol's user avatar
  • 71.5k
7 votes

Why is potassium less dense than sodium?

Although I liked James Gaidis's answer, I do not agree with some of arguments because they are all parts of one or more continuous trends. For instance, look at the melting points and boiling points ...
Mathew Mahindaratne's user avatar
6 votes
Accepted

In Bohr's model what is angular momentum in the lowest orbital?

You are trying to mix the Bohr model with quantum mechanics. The Bohr model is a semi-classical treatment of the hydrogen atom in which an electron is circling around a proton. Classically, this ...
Paul's user avatar
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6 votes
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How were the Hoffman's and the Zaitsev's rule formulated even before the discovery of the electron?

This excerpt is from an article in J Chem Ed (J. Chem. Educ., 1961, 38 (6), p 297 DOI: 10.1021/ed038p297) describing the contents of Markovnikov's 1870 paper in Liebig’s Annalen (translated into ...
Karsten's user avatar
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6 votes

Bohr's model of an atom

Think of the planetary system which inspired Bohr to think about his atomic model. The Earth is rotating around the Sun in a fixed orbit. What keeps the Earth rotating around the Sun? The mechanics of ...
ACR's user avatar
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6 votes
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Magnetic moment of trivalent lanthanide cations

Your question, Why can't we use normal formula to find effective magnetic moment of tripositive rare earth elements (REs)? is answered excellently by porphyrin' comment (vide supra). Thus, I won't ...
Mathew Mahindaratne's user avatar
6 votes

Does electron mass decrease when it changes its orbit?

Does electron mass decrease when it changes its orbit? Essentially yes. If you add the mass of a free proton and a free electron you'll get a greater mass than that of a hydrogen atom. The mass ...
MaxW's user avatar
  • 22.3k
6 votes

What is the radial probability distribution function and what is its significance?

Imagine a tango party with a large dance floor and a single porta-potty (one square meter floor area). There is a larger chance of finding people on the dance floor than in the restroom. On the other ...
Karsten's user avatar
  • 40.8k
6 votes

Lother Mayer curve

It is an interesting question, and I am not completely sure on everything I write below. First of all, atomic volume is defined as the "quotient obtained by dividing the atomic weight of an ...
S R Maiti's user avatar
  • 5,685
6 votes
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Could a positron be made to stably orbit an atom?

Positron chemistry is a thing, though experimental lifetimes are in the nanosecond range due to annihilation. The noble gases seem to have a relatively favourable electron configuration, reserving a ...
Pallas's user avatar
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