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 ...
- 39k
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 ...
- 40.2k
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 ...
- 39.1k
17
votes
Accepted
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 ...
- 482
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 ...
- 31k
15
votes
Accepted
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 ...
- 71.1k
14
votes
Accepted
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 $\...
- 71.1k
13
votes
Accepted
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 ...
- 71.1k
12
votes
Accepted
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 ...
- 30k
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. ...
- 30.3k
11
votes
Accepted
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.
...
- 30k
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, ...
- 28.3k
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 ...
- 35.4k
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 ...
- 20.8k
8
votes
Accepted
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 ...
- 13.9k
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$...
- 1,614
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....
- 1,983
7
votes
Accepted
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 ...
- 22.3k
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 ...
- 71.1k
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 ...
- 39.5k
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 ...
- 2,396
6
votes
Accepted
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 ...
- 39.1k
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 ...
- 39k
6
votes
Accepted
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 ...
- 39.5k
6
votes
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 ...
- 39.1k
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 ...
- 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 ...
- 39.1k
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 ...
- 5,637
6
votes
Accepted
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 ...
- 717
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