41
votes
Is there radioactivity at absolute zero?
Theoretically, a radioactive material will still be radioactive at absolute zero, and its rate of decay will be $100.00\%$ of that at room temperature. Practically, at the lowest achievable ...
- 29.9k
40
votes
Accepted
What roles do neutrons play in an atom?
Neutrons bind with protons and one another in the nucleus through the strong force, effectively moderating the repulsive forces between the protons and stabilizing the nucleus.$^{[1]}$
$\ce{^2He}$ (2 ...
- 23.3k
35
votes
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How do I visualize an atom?
I have searched and searched, oh how I have searched.
Do you know what I always tell my mom when she asks me to find something in the Internet she was not able to find herself? I ask her: "Are you ...
- 18.5k
25
votes
Accepted
Is it possible to speed up radioactive decay?
It is possible to modify nuclear decay rates using chemistry, though it is rare and the effect is usually very small. Here I summarize the information available in this link. You may want to see the ...
- 26.2k
22
votes
What is SPDF configuration?
s, p, d, f and so on are the names given to the orbitals that hold the electrons in atoms. These orbitals have different shapes (e.g. electron density distributions in space) and energies (e.g. 1s is ...
- 82k
22
votes
What roles do neutrons play in an atom?
In a few more words, physicists right now are confident in saying that there are four fundamental things that happen:
Protons and neutrons stick together. (The "strong nuclear interaction".)
Neutrons ...
- 321
21
votes
Accepted
Do acids really donate a proton?
Yes, according to the Arrhenius theory, acids dissociate in aqueous solution and release a proton ($\ce{H+}$). The Brønsted–Lowry defines acids ($\ce{HA}$) and bases ($\ce{B}$) in such a way that ...
- 43.1k
20
votes
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Why six C atoms are usually seen in cyclic compounds?
It is all about minimizing the energy of a molecule.
In the case of carbon, the only molecule that adopts a perfect hexagonal geometry in its ground state is benzene (and its derivatives that possess ...
- 82k
19
votes
Why were elements discovered "out of order" after 1950?
The synthetic trans-uranic elements (the "modern era" elements as you call them) are synthesized by bombarding a certain isotope of one element with a certain isotope of another element with a lot of ...
- 2,992
18
votes
Accepted
Why do atoms "want" to have a full outer shell?
You are attaching too much importance to Lewis structures. The 8-electron rule and Lewis structures which are derived from it are only rough guidelines for working out the electronic structure of a ...
- 17.3k
18
votes
Accepted
Why are the masses of atoms less than the sum of their subatomic particles?
This is due to the mass-energy equivalence and a phenomenon called binding energy.
Forming a nucleus releases energy because the nucleons are falling into a potential energy well. Due to Einstein's ...
- 14.9k
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 ...
- 30.3k
17
votes
Protons and the Heisenberg principle
But in the case of protons, we are kind of certain about their
position in the atom.
Well, yeah, kind of certain. The very notion of molecular geometry arises in the Born-Oppenheimer approximation. ...
- 18.5k
16
votes
How do I visualize an atom?
I am looking for a 3 dimensional visualization of a whole (moderately complex, hydrogen is just a ball) atom that includes 3 dimensional orbital geometry.
3 dimensions is only enough to represent the ...
- 38.9k
16
votes
How did Mendeleev know elements from compounds or mixtures?
Please do not underestimate the scientists of 19th century. They were as creative, intelligent and perhaps more genuinely dedicated to science than the scientists of the 21st century. Spectroscopy was ...
- 32.7k
16
votes
Why do electrons jump back after absorbing energy and moving to a higher energy level?
This is a very fundamental question and for really understanding the "why" some advanced physics is involved. I will describe the process rather superficially.
As you might know, the level ...
- 2,306
15
votes
Accepted
What actually is the Wavefunction?
Let me see if I can get at some of your questions. As mentioned above, it's much easier when you ask individual specific questions.
One problem with books on introductory quantum mechanics is that, ...
- 26.9k
15
votes
Accepted
While filling electrons, we follow Aufbau principle, but not while removing them. Why is this so?
Usually when adding electrons based on the Aufbau principle, you go from one element to the next highest one, e.g. from $\ce{Ti}: \ce{[Ar] 4s^2 3d^2}$ to $\ce{V: [Ar] 4s^2 3d^3}$. Thus you add not ...
- 4,514
15
votes
Accepted
Why is the electron-nucleus attraction modelled with only electrostatic interactions?
If I understand the question correctly, OP is somewhat surprised that Coulomb's law is used to describe the interaction between an electron and a nucleus, although it is usually pictured that ...
- 18.5k
14
votes
Accepted
What holds atoms together?
In non-nuclear chemistry, everything is electrostatic interactions. This is why you can learn and predict so much just by "following the electrons"
Covalent bonds are also formed because of ...
- 10.1k
14
votes
Accepted
Why is Astatine monoatomic?
One key problem with astatine is that it's incredibly unstable. There are no known stable isotopes, and the longest-lived has a half-life of ~8 hours. So no one has been able to (yet) prepare enough ...
- 26.9k
14
votes
Deflection of Alpha Particles in Rutherford's model of atom
See, what the Geiger-Marsden-Rutherford experiment achieved was the following: by bombarding (with alpha particles) a one-atom thick gold sheet and counting how many alpha particles passed through, ...
- 2,833
14
votes
Accepted
Why are dipoles "permanent/induced dipole permanent/induced dipole" and not just "permanent/induced dipole" once?
Because it takes two to tango.
Dipoles interact with each other. A Lone dipole has nothing to interact with (other than an electric field, but if we ignore some externally applied macro field, there ...
- 32.2k
14
votes
Accepted
Can Rydberg constant be in joules?
Authors may be sloppy about notation in this matter. I recommend considering $R_\ce{H} \approx \pu{10973 cm-1}$ and $Ry \approx \pu{2.18e-18 J}$, noting $Ry = hc \cdot R_\ce{H}$. Units of wavenumbers $...
- 2,155
13
votes
Why was atomic mass scale changed from Oxygen - 16 to Carbon - 12?
The mass scale has changed over time, largely due to different isotopes of the "baseline." Not surprisingly, there's a good Wikipedia article on the matter.
In the 20th century, until the 1960s ...
- 26.9k
13
votes
Is the atom the smallest particle, which takes part in chemical reactions?
Protons definitely participate in chemical reactions. Free protons are generally not present in liquid water because a free proton is extremely reactive, but in the upper atmosphere or in other ...
- 38.9k
13
votes
Why do atoms need 8 electrons to stabilize?
The valence orbitals of atoms are composed of suborbitals (s and p) there is 1 s suborbital which is spherical and can hold 2 electrons (one with up spin and one with down spin). There are 3 p ...
- 11.9k
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