116
votes
Why can atoms only gain or lose electrons and not protons?
The energy required to remove an electron from an atom is called its ionization energy. Typical ionization energies are five or ten electron-volts. A visible-light photon carries an energy somewhere ...
rob♦
- 89.9k
108
votes
Accepted
How do we know neutrons have no charge?
Free neutrons in flight are not deflected by electric fields. Objects which are not deflected by electric fields are electrically neutral.
The energy of the strong proton-neutron interaction varies ...
rob♦
- 89.9k
98
votes
Accepted
Are protons bigger than electrons?
Quantum mechanical particles have well-defined masses, but they do not have well-defined sizes (radius, volume, etc) in the classical sense. There are multiple ways you could assign a length scale to ...
83
votes
Accepted
Why are protons heavier than electrons?
There are multiple reasons why protons are heavier than electrons. As you suggested, there are empirical and theoretical evidence behind this. I'll begin with the empirical, since they have important ...
77
votes
Accepted
Can there be an atomic nucleus where there are more protons than neutrons?
What you are looking for is isotopes with neutron–proton ratio N/Z less than 1. You can find these isotopes, for example, in this list from Wikipedia. As you can see, you are looking for members of ...
69
votes
Why are protons heavier than electrons?
As noted "why" is a tricky question but we may ask what is the most fundamental view known concerning this question.
Electrons and protons are very different beasts. Electrons as far as we can tell ...
61
votes
Why doesn't an electron ever hit (and stick on) a proton?
The electron and proton aren't like pool balls. The electron is normally considered to be pointlike, i.e. has no size, but what this really means is that any apparent size we measure is a function of ...
57
votes
Theoretically, could there be different types of protons and electrons?
Your friend is correct: there's only one type of proton.
The proton is the lightest baryon. It has charge $+1$, spin $1/2$, and baryon number $+1$.
These three quantum numbers are so fundamental ...
57
votes
Why the charge of the proton does not transfer to the neutron in the nuclei?
A proton can exchange charge with the neutron via a process called "pion exchange". In this process, the proton with quark content $uud$ sends a positive pion $u\bar{d}$ over to the neutron $...
49
votes
Why the charge of the proton does not transfer to the neutron in the nuclei?
If I put a red billiard ball and a blue billiard ball in a bag, leave them for a while, and then draw one out, I will find I am holding a red ball or a blue ball. Never a purple ball.
At the level of ...
48
votes
Accepted
Can an electron and a proton be artificially or naturally merged to form a neutron?
The one-word answer is yes.
You are also correct that the neutron is not just a proton and electron living together. The process of merging a proton and electron proceeds via the weak force. ...
47
votes
Accepted
Theoretically, could there be different types of protons and electrons?
It is an experimental fact that all electrons and also all protons (but this often applies also to nuclei, atoms and even molecules) are indistinguishable from one another, i.e. they both are ...
45
votes
Accepted
Why can atoms only gain or lose electrons and not protons?
If an atom gained a proton, it would become a different atom. For example, if a hydrogen atom gained a proton, it would become a helium atom (for a sec forget that helium which you find in nature has ...
44
votes
Accepted
What is the experimental evidence that the nucleons are made up of three quarks?
What is the experimental evidence that the nucleons are made up of
three quarks?
Some strong pieces of evidence for the quark model of the proton and the neutron, not stated in another answer, are ...
44
votes
Can there be an atomic nucleus where there are more protons than neutrons?
According to Wikipedia:
Other than protium (ordinary hydrogen), helium-3 is the only stable isotope of any element with more protons than neutrons.
41
votes
Why does this quiz question say that protons and electrons do not combine to form neutrons?
You're asking about two distinct phenomena. The difference between them is subtle, and I think there is some context missing from the second question that you quote, which makes things more confusing ...
rob♦
- 89.9k
40
votes
How is Alpha Radiation possible?
It's definitely not the case that the electron cloud is undisturbed. The process is quite violent on the scale of the atom undergoing alpha emission.
The electron cloud is excited by the process of ...
39
votes
Accepted
Proton: 2 up, 1 down quark, Neutron: 2 down, 1 up, how can Neutron: proton + electron?
A neutron is not "a proton and an electron". A neutron is not composed of a proton and an electron inside of the neutron.
In quantum mechanics, particles can appear and disappear or change into other ...
33
votes
Why are protons heavier than electrons?
It's just an empirical value. According to our current knowledge, the masses actually come from some more fundamental quantities - the electron yukawa coupling and the Higgs field vev, in the case of ...
33
votes
What is the experimental evidence that the nucleons are made up of three quarks?
Note that the original SU(3) quark model was entirely mathematical (The Eightfold Way) and was a brilliant way to explain the observed spectra of baryons and meson. The whimsically named quarks were ...
33
votes
Accepted
How is the speed of nucleons in the nucleus measured?
If you shoot an electron or a proton at a nucleus at moderate energies (a few hundred $\mathrm{MeV}$ to a few $\mathrm{GeV}$) it will usually either bounce off the whole nucleus or break up the ...
33
votes
Why no proton microscopes? Proton diffraction; or proton scattering experiments? Proton crystallography?
What do protons offer that electrons and photons don't? Well, mass:
$$ \frac{M_p}{m_e} \approx 1837 $$
What that means is that protons can travel through large $Z$ materials without undergoing ...
33
votes
Are some protons more massive than others due to spinning at a different rate or being in a more excited state?
No. Protons are indistinguishable particles; they all have the same mass, exactly.
We like to tell beginning students that the proton is “made of three quarks,” analogous to the way a hydrogen atom is ...
rob♦
- 89.9k
33
votes
Accepted
Why so much kinetic energy inside a proton?
The simplistic answer is that a proton is very small. The quarks are not free, but are confined to a small region. By the uncertainty principle a small uncertainty in the position of the quarks ...
28
votes
Accepted
Position of protons and neutrons in a nucleus
This does not violate the exclusion principle because the exclusion principle merely states that there cannot be more than one fermion in the same quantum mechanical state. In the case of two protons ...
28
votes
Is the nucleus smaller than the electron?
The question confuses the electron "cloud", which is really the probability for where an electron may be found, with the size of an electron. The electron is sizeless, which can either be ...
27
votes
Accepted
What is the reason for the shift in balance between neutrons and protons in the early universe?
There are two very relevant facts that inform this answer: (1) The rest mass energy of a neutron is 1.29 MeV higher than that of a proton. $(m_n - m_p)c^2 = 1.29$ MeV. (2) The total number of neutrons ...
27
votes
What happens if an electron and a proton fall into each other?
They would form a hydrogen atom.
They would not merge, because merging would result in a neutron, which is heavier than a proton and an electron combined. However, if they are sufficiently forcibly &...
26
votes
Accepted
Are some protons more massive than others due to spinning at a different rate or being in a more excited state?
The word proton is used differently in these two quotes.
Physicists use proton only for the three-quark baryon itself. Chemists sometimes use the term proton as a shorthand for a chemically bonded ...
24
votes
Why doesn't an electron ever hit (and stick on) a proton?
This was a big mystery before quantum mechanics was discovered. Not only are electrons attracted to protons, electrons radiate away energy when accelerated. A classical electron in orbit around a ...
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