I meant: Why is the universe created with atoms that have negatively charged particles on the outside of the atom instead of at the nucleus with a neutral charged particle orbiting?
Actually, in certain circumstances, they can, and it is called electron capture. So, why don’t they more generally? The important reason lies in quantum mechanics, and that is when the electron is in a stationary state, it cannot radiate energy other than by falling to a lower state. What that means is that in the ground state, say, of hydrogen, the electron cannot radiate energy and drop to a lower energy, so it is stuck with its current kinetic energy. The only way it could convert a proton to a neutron is if its kinetic energy is sufficient to overcome the energy barrier to converting a proton to a neutron. That barrier, from mass difference, is a little over 1.29 MeV. The ground state energy of the electron in hydrogen is a little under 13.6 eV, so the reason it does not convert the proton to a neutron is that it has about five orders of magnitude too little energy to do it. The reason electron capture happens with very heavy elements is that the 1s electrons have relativistic energy, AND when absorbed, there is an increase in nuclear binding energy, so there is a helping hand on the energy front.
The important point is that as the electron approaches the proton for an instant, it does not change energy. Very specifically, its action is quantised, which means its energy divided by wave frequency is constant, and the wave frequency cannot change other than into a lower stationary wave, and there is none available. Therefore the energy behaves as if constant.
That question was a major mystery in the early days of quantum physics, and it deeply bothered many of the early great physicists. The answer turns out to lie in quantum physics, and the fundamental reason is that the electron is light in its weight, its mass. If you try to squeeze it into a small space, you reduce its size and therefore its wavelength; but according to quantum physics, if you reduce its wavelength you increase its momentum and its kinetic energy, so it escapes.
Here are the simple equations: let the size (wavelength) of the electron be . Then the momentum of the electron is , and the kinetic energy is . Small size means high kinetic energy.
There is a particle very similar to an electron called a muon; but it is 207 times heavier. That means you can squeeze it to a smaller size without giving it more momentum. (Play with the equations I gave, making the mass m 207 times bigger, to see how small you can squeeze it for the same kinetic energy.) We do indeed form muonium atoms in the lab, and they are indeed much smaller than are hydrogen atoms, beautifully confirming the theory.
Forget the satellite analogy. It's wrong, quite wrong.
Subatomic "particles" are not particles at all, nor are they waves. They are what they are, and have simultaneously some properties of waves and particles.
The electrons in an atom desperately want to stick to the nucleus, but they can't. Think of them like standing waves wrapped around the nucleus. They can only exist in even numbers of wavelengths, and they cannot occupy the same space. So they like to sit as close as they can to the nucleus, but they can never reach it. Now wrap that idea around in three dimensions, and you have a pretty good idea of the reality.
Add to this that the protons in the nucleus are strongly repelling each other, but are held together by a stronger force that acts only at extremely short range--the well-named strong nuclear force. Neutrons act as spacers to make the mutually repulsive protons chill out a bit and help the strong force overcome them and hold them together. This is why firing neutrons at atoms is a good way to cause nuclear fission--knock a neutron out of place and the nucleus may just break into pieces.
Actually, they do sometimes join with the protons at the nucleus of the atom. As a result, an electron is lost, a neutron is formed and neutrino is emitted. This process is called "electron capture" and it's very important in a kind of radioactive decay called "beta decay". Two example isotopes where this sometimes happens are potassium-40 and beryllium-7. This also is important in the formation of a neutron star during a supernova. A better question might be: Why doesn't this happen more
often?
The electron capture reaction involves the "Weak Force", one of the four fundamental forces in the Standard Model. Specifically, a proton emits a virtual W+ boson, which is absorbed by the electron. From this a neutron is formed and a neutrino is emitted. Two things determine the rate of this reaction: First, the electron has to be in the nucleus in the first place. How often is it there? It is known that the innermost electron shells will undergo electron capture most often. This makes sense because the orbits of these electrons are spherical and overlap the nucleus quite well. The innermost shell is called the K-shell and for this reason, electron capture involving this shell is called "K-capture". During the collapse of star, gravity tries to overcome the Pauli Exclusion Principle and the electrons get really, really packed together. This is why the rate of electron capture is so high during a supernova. Second, the nuclear reaction has to be energetically favored which is not a common situation. So in normal isotopes, it happens pretty much never. In the case of the unstable, neutron-rich nuclei that I listed above, things are more energetically favored so it happens much more often, which is still almost never.
As for your second question, the neutrons in the nucleus are bound there by another one of the fundamental forces, the "Strong force". The most important aspect of this force is that it gets stronger the further apart two things bound by it become. This is kind of like how a rubber band pulls harder, the more it is stretched. This force binds both the neutrons and the protons in the nucleus. The electrons do not feel this force, so they are free to have orbits that are much, much larger.
Two completely different questions! I’ll answer them in order:
- Excellent question, which everyone asked themselves as soon as Rutherford discovered that the “plum pudding” model of the atom was wrong. The answer was stupefyingly unexpected: quantum mechanics. (Which see.)
- Who knows why the universe was “created” the way it was? Furthermore, what would make a neutral particle “orbit”? Not gravity, that’s for sure — it’s several dozen orders of magnitude too weak. This question makes no sense to me.
The fact that matter is stable is because electrons do not fall into the nucleus. Classical physics cannot explain why matter is stable as it requires the orbiting electrons to lose energy and fall into the nucleus. Quantum mechanics comes to the rescue. The electron in the hydrogen atom for example has a potential energy which depends only on the distance of the electron from the nucleus. The Schrodinger equation in quantum mechanics then tells us that the electron in the hydrogen atom is in a stationary state, meaning that it doesn’t lose energy and fall into the nucleus. This is the quantum mechanical explanation for the stability of matter.
Question: In an atom, why do the negatively charged particles orbit the atom instead of joining with the protons at the nucleus of the atom?
Disclaimer: I am not a physicist, but I like to reason: take this answer with a grain of salt. This answer supposes the reader has a basic knowledge of quantum mechanics on the level of a college freshman in Chemistry.
Like the other Chemists have already answered (but none of the Physicists, it seems), it does happen that an electron is “swallowed” by the nucleus. In fact, I was taught already in 9th grade that the mass of a neutron is the mass of a proton plus the mass of an electron, and it makes sense.
I have a very simplistic view of nuclear physics, and atomic physics in general, but I wager that if you solve the relativistic Schrödinger equation (Dirac equation) for any heavy element where you treat all neutrons as protons, you will find that some electrons are so tightly bound to the nucleus (much more tighly bound than what one typically refers to as the “core electrons”) that for all purposes, the nucleus has a reduced charge. It is this “reduced charge” version of the nucleus that typically goes into solving the electronic structure (with the corresponding reduction in the number of electrons).
This very simple model explains why He-2 is not stable (it should reduce to deuterium by radioactive decay as one of the electrons falls into its groundstate in the nucleus). It also suggests why the ratio of protons to neutrons keeps decreasing as you increase the atomic mass (remember, treat the neutrons as protons and more and more electrons will be “sucked in” in the groundstate). It is not a “correct” model, however, since there is no place for the neutrino (in this simplistic model, it would simply be a high-energy photon), but I am not a particle physicist and so I can get away with that.
Note: it has to be the Dirac equation, because the non-relativistic Schrödinger equation is not useful at the speeds that these electrons will acquire. Since I have not actually solved the Dirac equation for a Coulomb potential, I cannot be sure that this is what it will predict. There is also the possibility that the gist of the model is correct but that the Coulomb potential must be augmented with some other (strong and short-ranged) force in the nucleus.
There are a few main reasons as to why the electrons do not join the protons in the nucleus of an atom. This is the basic quantum theory definition though, and does not go into the more complex matters regarding quantum mechanics.
- The electron is so small that is barely registers on the scale of the protons and the neutrons. You need to understand that the electrons do not "orbit" the atom as a planet might orbit a star. The electron goes anywhere within its orbital, which is a vague zone that the electron(s) tends to stay in. Because the electron stays in its orbital, and also because it barely registers on the magnitude scale of the protons, it will not simply "join" the protons in the nucleus.
- In most cases, there are many electrons as well as many shells in an atom. The electrons are attracted towards the protons in the nucleus, but electrons in the same shell would feel the same attraction. The shell as a whole is brought towards the nucleus, but in the end the repulsive forces between electrons overcomes the attractive force of the brotons because the electrons cannot get any closer.
- There is an effect in atoms with multiple electron shells called electron shielding. This means that, as each consecutive shell is further away and has more shells between it and the nucleus, the electron shells closer to the nucleus will effectively create a "shield". This shield insulates the outer electrons from the forces of the protons in the nucleus, resulting in the outer shells feeling less attraction.
These points do not cover everything, but together provide a fairly thorough basis for the reason as to why the negatively charged particles do not join the protons in the nucleus of an atom.
I will start from the very beginning.
According to Coulomb's law, a positive and negative charge particle attract each other with a force called electrostatic force. Also, a positive and positive charge particle repel each other and a negative and negative charge particle repel each other with a force called electrostatic force. To experience this force, there should be a test charge and a charge producing electric field.
So, now let us come to the question.
Positively charged nucleus is producing electric field and test charge is an electron. As an electron is not at rest but in motion, net centripetal electrostatic force will be balanced by m v .v / r. If an electron were at rest, it would be attracted by the nucleus and finally falling into it. Well, things are not that way. Nature has maintained balance.
Theoretically and practically, it has been found that an electron can never reside inside the nucleus according to Heisenberg's Uncertainty Principle. So, it is actually orbiting around the nucleus and an atom is stable by these balancing forces. That's it.
Wait, if you are thinking this model I described above is the correct model, then you are mistaken. That is just the classical approach and now quantum physics will tell the complete truth.
An electron is neither orbiting around the nucleus in circular path nor in an elliptical path. The motion of an electron is similar to bee hovering around her honey. This is the updated model.
Bohr told that in spite of being accelerated ( centripetal acceleration ), an electron does not emit radiation. It does so only when it falls from higher level to lower level.
It was actually thought that an accelerated charge produces electromagnetic radiation and so while orbiting, an electron will lose energy and finally fall into the nucleus. This confusion led to Bohr's accepted proposal.
And finally, as other answers have mentioned, neutrons in the nucleus balance the repulsive forces between proton-proton by generating strong nuclear force which are short range forces and these forces exist between proton-proton too when they are close enough to generate nuclear force.
I like the stochastic electrodynamics explanation (SED). This is a classical theory of physics that is a good approximation of quantum physics under some conditions. SED says that the electron in the atom undergoes random acceleration due to electromagnetic waves that have a Lorentz invariant spectrum.
The random boosts given to the electron prevent the electron from combining the the proton. The Lorentz invariant radiation provides the energy necessary for the electron to retain its orbit. However, the electron is simultaneously emitting energy due to Bremsstrahlung emission. So the electron is in energetic equilibrium only at the orbital distances that can be determined by the currently popular quantum theory.
https://arxiv.org/pdf/1511.02083...
‘It is easy to calculate the behavior of a linear dipole oscillator in classical zero-point radiation.[10][11] The dipole oscillator radiates away its energy but it also picks up energy from the random forces of the classical zero-point radiation and so comes to a steady state probability distribution for energy, amplitude, and velocity. Using classical zero-point radiation, it turns out that Casimir forces, van der Waals forces, blackbody radiation, low- temperature specific heats of solids, and diamagnetism all come within the framework of this classical theory.’
According to classical mechanics it does fall into the nucleus!( which, obviously practically doesn’t). You must have studied the Thomson model of atom; if not just go through it. (I am assuming that you have studied it and giving you the answer!) According to Thomson the electrons are revolving around the nucleus with an acceleration. Now it is obvious that the electrons’ velocity is changing with time and according to classical mechanics any accelerating charge particle will radiate out the energy in the form of electromagnetic radiation(which is doesn’t). If such thing happens then the electron will surely depleting his energy and he should end in nucleus! But it cannot happen. Why? Let me say there works the HEISENBERG’S UNCERTAINTY PRICIPLE. Let me make clear how does it work in case of electron. Suppose the electron is moving towards the nucleus by the attracting force of the proton. Thus we can (safely!) tell that it’s velocity(and hence kinetic energy) is increasing constantly, while its potential energy is decreasing. Gradually there will come a time when the kinetic energy of the electron will goes off to positive infinity and it’s potential energy will reach off to negative infinity. When or more precisely at the moment electron will reach inside the nucleus {to marry proton!! :) } it’s kinetic energy will be positive infinite. So what does that has to do with Heisenberg’s uncertainty principle? Well, if you know the statement of Heisenberg’s uncertainty principle it says: “ The position and momentum of the particle cannot be measured simultaneously with accurate precision”. Hence when the electron end into nucleus it’s velocity is positive infine, means its uncertainty in momentum will also be infinite leading us to absolutely zero uncertainty in position. Now this is the property of a particle; a precise position. It means that electron became localized. But experiments says that it is not localized and behave like a wave and not a particle in atom. Hence, it cannot exist in nucleus. One more explanation should be that that the size of the nucleus is about femto meter. i.e. 10^-15 m. This means that the maximum uncertainty of the velocity of the electron mustn’t exceed this value but if you will calculate the uncertainty using Heisenberg’s uncertainty priciple purting (delta x) =10^-15 m you will get the uncertainty in velocity which is even greater than the speed of light i.e. of the order of 10^10 m/s, which electron obviously cannot possess. Hence electron cannot stay or go into the nucleus. Moreover, the positive and negative infinity in kimetic and potential energy respectively as mentioned above will counterbalance each other and hence will form a stable electron cloud at a definite radius; the so called bohr radius and electron will revolve around the nucleus maintaing his energy and the bohr radius and will not fall into the nucleus. For easy understanding follow the below link:
Question:Why do electrons revolve around the nucleus and why don't they form a "cluster" in the nucleus just like protons and neutrons and why neutrons or protons don't revolve around the nucleus instead?
(Note:The original question was improperly phrased and so meant something else entirely while the person who asked the question was seeking answer for the above question)
Let me take you back to the beginning of the universe "The Big Bang" as it is called. Immediately after this event occurred there was a sudden and enormous expansion after the rate of this expansion slowed down our Universe was composed of a quark gluon plasma which also consisted of other particles like leptons. There are 6 types of quarks up, down, strange, charm, bottom and top. All these exist in pairs the most stable of them being up and down quarks all other quarks decompose into up and down quarks very fast.
These quarks join together to form different types of particles the most significant being protons and neutrons. A proton is composed of two up quarks and one down quark while the neutron is composed of two down quarks and one up quark. An up quark on combination with an electron (electrons belong to the class of particles called leptons light(photons) is also another example of a lepton) changes to a down quark with the release of an electron neutrino which is another type of a lepton.
Now a proton is made of two up quarks and one down quark if one up quark from it changes to a down quark we get a neutron. Similarly when a lepton collides with a proton in this plasma created during the Big Bang it changed into a neutron. The opposite reaction is also possible. Now as you can see this is what happens if protons and electrons come together. Thus even if they did then they wouldn't leave any mark due to this reaction. The chance for such a reaction is greater when the nucleus hasn't been formed yet. When the nucleus is formed the chance for the reaction decreases. Now I told you why electrons cannot be present in the nucleus.
Now why can't neutrons orbit the atom instead. Do you have any idea about its mass. The mass of a neutron and proton is approximately 2000 times that of an electron. An object with a small mass can be easily accelerated and stopped and its path can be changed but with a greater mass it is much harder and it has a greater tendency to either move in a straight line than orbit the atom. This is why an electron orbits the nucleus and not any of the heavier particles.
The nuclear or planetary model had many limitations and this was one of the limitations of Rutherford's model. The classical theory of thermodynamic said that every charged particle emits radiation and looses energy so according to this theory the electrons would have to loose energy and collide with nucleus which had proton.
But, inorder to overcome the limitations of this theory Neils Bhor came up with quantized shell model. And the postulates suggest that the orbits have fixed energy level and electron holding capacity so the classical concept of thermodynamic would not come into use in case of atoms and also even if any energy is provided to an atom then the electrons do get excited and jump to other orbits in terms of quanta but only from lower energy level to higher but there is no case that the electrons can get into orbits which are below its own orbit so although the first orbit consists of the closest electrons, the electrons might jump up to other orbits but not to nucleus.
The following answer was given by me,for previous question,almost the same.It includes the answer to yor question, just think about it.
For sure this kind of question is answered by me before more than one time. Any way to make it clear we should remember the first question,it is, how the electrons,as charged particles, are moving in circular orbits around the nucleus,but not radiationg energy and then falling into the nucleus as classical physics assumes this? .The answer was given by the quantum theory of Niels Boher in 1913.In this theory Bohr proposed:
1-Each electron is moving in a certain orbit does not emit any radiation.
2- It emits or absobs radiation when it changes its orbit up or down.
3-Its total anguler momentum is quantized given by L=nh/2pi ,where n is the pricipal quantum number, n=1,2,3,----and h is Planck constant.This is how the electrons are physically working according to the quantum physics principles. Now,What are the forces acting on the electron?thee forces are the electrostatic force and the so called the centrifugal force,they are equal and in opposite direction.The centripetal force is given by F=mV^2/2 and the electrostatic force is Fe=CZe^2/r^2,.Where C is constant,Z is the atomic number,V is the velocity, m is electron mass,e is the charge and r is the radius of the atom.It is possiple to find the energy of n orbital state to be En= -13.6Z^2/n^2 eV.
This is how electrons are moving in their shells around the nucleus,under the balance of the two forces.
Well let's do a little maths with some
Quantum physics
Ok , for the negatively
Charged particles to be in the positively charged nucleas the uncertainty in their position must be about
10^-15 m ( in order of centimeters )
Now,According to uncle Berg' s( Heisenberg) uncertainty principal
The product of uncertainty in position
and uncertainty in velocity of a particle
is always greater than
Planck's constant divided by 4pi times the mass of the particle
Using these values you
Will find that the uncertainty in the velocity of the particle come out to be more than even the speed of light, that is
for the particles to be in the nucleas their velocity must be completely uncertain
Which is absurd so that's why electrons (your negatively charged particles )cann' t be in the nucleas
Hope this will help.
There is no particular reason why electrons should go around a positive nucleus instead of protons going around a negative nucleus.
The system (nucleus + electrons) is bound due to electro magnetic forces (there are other forces but let's keep it simple). . . that they don't fall apart on their own. It's as simple as the gravitationally bound earth sun system. It's just that earth is much much lighter (mass of earth << mass of sun) that the CoM of earth sun system is inside the sun and so the earth does most of the “going around” . . . I mean moving. Although the sun is affected a bit . . . . it wobbles a bit but that wobbling is way too less to be called as “revolution of the sun around earth”.
Same is the case with electron nucleus system. Gravitational interaction replaced by em interaction, sun replaced by the nucleus and electron replaced by the earth.
If, however, the nucleus is replaced by a negative muon and the electron by a positive muon of similar mass, then both the positive and the negative muon would go around a common CoM.
Having said the above, it is not easy to analyse such atomic systems in the realms of classical physics. Thanks to a weird behavior called quantum behaviour that gives rise to all the variety that we see, including you and me !
First. The electron orbits the nucleus because the neutron has it's blocking field and the nucleus has higher mass so the Gp potential is creating velocity witch then turns to a higher velocity then the gravity witch creates a electron orbit.
Sometimes the electron loses velocity and is pulled by the nucleus and that creates positive charge.
This is not that compclitated.
Because they’re tiny, and moving very fast; so the electrons basically keep missing the protons.
And if they get close enough, they end up in orbit around each other; likewise, electrons repel other electrons, so they keep each other apart.
That’s where we get atoms and molecules.
This is why in the entire history of the universe, there’s only about as many neutrons as protons: i.e. half of them have been consistently missing each other for 13.8 billion years, despite mutual attraction….. meanwhile the other half didjoin to form neutrons.
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