Electrons Definition and 998 Threads

The electron is a subatomic particle, symbol e− or β−, whose electric charge is negative one elementary charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ħ. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavelength for a given energy.
Electrons play an essential role in numerous physical phenomena, such as electricity, magnetism, chemistry and thermal conductivity, and they also participate in gravitational, electromagnetic and weak interactions. Since an electron has charge, it has a surrounding electric field, and if that electron is moving relative to an observer, said observer will observe it to generate a magnetic field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law. Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications such as tribology or frictional charging, electrolysis, electrochemistry, battery technologies, electronics, welding, cathode ray tubes, photoelectricity, photovoltaic solar panels, electron microscopes, radiation therapy, lasers, gaseous ionization detectors and particle accelerators.
Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms. Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge 'electron' in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897 during the cathode ray tube experiment. Electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere. The antiparticle of the electron is called the positron; it is identical to the electron except that it carries electrical charge of the opposite sign. When an electron collides with a positron, both particles can be annihilated, producing gamma ray photons.

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  1. Y

    Are Electrons Not Part of an Atom?

    This will probably sound stupid to a lot of you on here, but I'm a little confused, and this is my first time learning this stuff. So electrons aren't part of an atom is that correct?
  2. I

    What is the force that hold the electrons?

    "Inside an insulator, the electrons are tightly held by nuclei." What is the force that hold the electrons? I found out from the Internet that insulators have strong covalent bonds inside and so electrons are tightly bounded to the nucleus. But in another source, it is stated that...
  3. I

    Why would our hands lose electrons easily?

    Our hands are high in the triboelectric series, which means our hands lose electrons easily. Is there a reason behind?
  4. A

    Why does valence electrons not produce electric field in the space?

    let X be any hypothetical isolated neutral atom and X- be the anion formed when X gain 1 electron this extra electron is in the valence energy orbit(band) and X- being charged produces electric field check me if i m wrng above now X(neutral) also consists of electrons in the...
  5. H

    Discovery of electrons - How did Thomson know they were particles?

    Greetings, I have been having some fun in the last couple of days by looking at the details of historically significant experiments. One such is Thomson's discovery of the electron, in which he concluded that cathode rays were, in fact, composed of negatively charged, discrete particles. But...
  6. D

    Understanding the Mystery of Electrons: The Laser Slit Test

    So the laser test with the slits is as followed as far as I understand. When observed, electrons act as particles. When not observed, electrons act as waves. How can electrons know if your eyes are open or closed? Unless your eyes give off some wort of radiation that it can pick up on...
  7. I

    Escape of Electrons from Nucleus: Frequency and Occurrence in Atoms

    escaping electrons... how easy is it for an electron to escape the nucleus of an atom and how often does it happen? say we have an atom of carbon, how often will it shed/share or swap an electron, or how often will an electron escape in an average time frame?
  8. E

    Threshold frequency and wavelength of electrons in the photoelectric effect

    Homework Statement Electrons are emitted from a metal as a consequence of their absorption of energy from a light beam. Find the threshold frequency of the metal and the wavelength of emitted electrons. Wavelength of incident light λ = 500 nm Work function of the metal \phi = 2.1 eV Homework...
  9. J

    Concentrations of electrons in intrinsic semi-conductor

    Hi, I've just started using the formula for the abovie which is given as: n t^3/2 exp(Eg/2kBT) however instead of n= I think the sign is n is proportional, like this ∞ I was wondering which would be correct? Thanks
  10. V

    Better explanation for why electrons in filled bands don't conduct?

    My book talks about it, but doesn't give a very intuitive reason why. It essentially says that from a modified version of Liouville's Theorem, the electrons in a band stay in that band. Then it says the phase space (position-wavevector phase space) has a constant density through time, and if...
  11. J

    What happens when you collide protons with electrons in a super collider?

    Does it just burst into vast amounts of energy? Or what about colliding two electrons together. higgs boson?
  12. A

    Electrons, Protons, Neutrons - Build-stones?

    Hello. You'll have to excuse my spelling (If I spelled anything wrong), I'm from Sweden and even though I'm told to be good at English, I'm not an expert. I literally just found this forum in my search for some kind of physics forum where I could ask the following question: Are electrons...
  13. D

    Collisions of electrons and alpha particles

    What would happen if one were to fire electrons at a solid mass of alpha particles?
  14. A

    Why are electrons so much stronger than protons

    In chemistry I remember learning that electrons and protons had equal but opposite charges but also that electrons were much smaller than protons. So how is it that something so much smaller can have an equal charge?
  15. A

    Atomic Absorption of Electrons: Mercury

    Homework Statement My class is currently going over electronic energy levels, and the book states that an electron with a kinetic energy of 9.8eV could excited two mercury atoms (first excited state above the ground state of mercury is 4.9) to their first state above the ground state...
  16. E

    A stream of protons and electrons

    A stream of protons and electrons are shot horizontally (from the left edge of the page to the right) with a speed of 1.2 x 10^6 m/s. A magnetic field is oriented perpendicular to this motion (upward, out of the page) with a magnitude of 1.225 T. What is the radius of the curvature and the...
  17. V

    Why does electromagnetic radiation (energy) excite electrons?

    Hello everyone, I've been told many times that when the right frequency of electromagnetic radiation hits an electron, it is excited to another energy level. My question is this, "why do electrons get excited to higher energy levels when hit by electromagnetic radiation?" Why does the...
  18. M

    Calculating the Relation between Electrons at Vakuum Level and Fermilevel

    I posted this in the math forum by mistake, so posting it here now instead Homework Statement The cutoff frequency for the photoelectric effect for silver is 1.089*10^15 Hz and its Fermienergy at T = 0 degrees Celsius is 5.5 eV. Calculate the relation between the number of electrons in...
  19. Y

    Delocalizing Electrons: Time and Diffusion Lengths in Conduction Bands

    Recently there was a discussion concerning whether an electron in the conduction band was localized or delocalized. The back and forth arguments seemed inconclusive, difficult to follow (too brief too couched in jargon/unrealistic models) and ended in something close to insults back and forth...
  20. S

    How Do Electrons Behave Between Charged Parallel Plates?

    Homework Statement An electron beam enters the region between two oppositely charged parallel plates near the negatively charged plate, as shown below. The plates are 0.150m long and are 0.040m apart. There is an electrical potential difference of 60.0V across the two plates which creates an...
  21. R

    Could Electrons Exist in 4 Dimensions?

    Greetings, This is basically just an observation I expect it to be laughed at (already has been laughed at in the mensa forum) but you know what they say - the only stupid questions are the ones left unasked and what better way to put it to rest than to ask some real hard core physicists... I...
  22. E

    Correlation energy between two electrons

    Hello. I need to find the expectational value of the correlation energy between two electrons which repel each other via the classical Coulomb interaction. This is given by the 6-dimensional integral: \left\langle\frac{1}{|\vec{r}_1 - \vec{r}_2|}\right\rangle...
  23. G

    Can Magnetic Attraction Between Electrons Overcome Electrical Repulsion?

    Since the magnetic force between dipoles goes as 1/r^4 and the electrical force goes as 1/r^2 for charges, would electrons be able to theoretically get close enough for their magnetic attraction to be greater than their electrical repulsion? If so, what then?
  24. S

    Flow of Electrons in Batteries: Current? Time?

    in a battery, when all the electrons have transferred to the positive terminal ( i mean both terminals have same no. of electrons) , then do any current flow? if no , then how much time does it take for all electrons to be transferred fron negative to positive terminal? (i know it is a silly...
  25. B

    I calculating the number of Electrons? (Current/Electron Density/Velocity)

    Homework Statement How many protons are in the beam traveling at the speed of light in the Tevatron at Fermilab, which is carrying 11.17 mA of current around the 6.3-km circumference of the main Tevatron ring? Homework Equations Not sure... The Attempt at a Solution I don't...
  26. K

    Physcially, how electrons choose the path with min resistance

    physcially, how electrons choose the path with min resistance if 2 paths of 2 differnet resistances electrons distributed & may if short circuit exist it take it how electrons know there is short circuit and how they know the path of min resistance ! Another question of a connection...
  27. D

    Electrons motion at de broglies wavelength

    Homework Statement When an electron moves with a certain de Broglies wavelength, does any aspect of the electrons motion vary with the wavelength. Homework Equations λ=h/p p=mv The Attempt at a Solution Ok so I realize that under certain conditions electrons wavelike properties can be...
  28. Y

    Electron Configuration for Multivalent electrons.

    I am trying to draw electron configurations for multivalent electrons for Pb4+ and Pb2+. The work I have: (Xe)6s24f145d10 (PB2+) (Xe)6s04f145d10 (PB4+) the problem I'm having with multivalent structures is: I have no idea which electrons to remove when there is an ionic charge For...
  29. T

    Number of K electrons that are ejected from lead

    Homework Statement Determine the number of K electrons ejected from a foil of lead with thickness 0.5 x 10^20 atoms/cm^2. It is bombarded by 10^4 photons that each have an energy of 88keV. Homework Equations From a figure in the book, it shows that u/p (7.483 cm^2/g = .7483 m^2/kg). I...
  30. G

    How to find the number of unpaired electrons?

    How do you find the number of unpaired electrons in a salt such as aluminum sulphate or ferrous sulphate. The number of unpaired of electron or bond order is needed to determine if something is paramagnetic.
  31. X

    Photon Emission from electrons and the EM field

    Ok, I've been reading up on the EM field and how it exerts force on charged particles. By exerting this force it creates 'ripples' in the EM field and this is felt by other charged particles as a force (either of attraction or repulsion). We say that the two particles exchanged a virtual photon...
  32. elementHTTP

    Exploring Decay of Electrons in Magnetic Field

    So i was watching Susskind lectures on entanglements http://www.youtube.com/watch?v=CaTF4QZ94Fk and there he mention decay (electron in magnetic field emits a photon whit certain probability ) That made me wonder : 1. How long you have to wait for emission to occur ? (for probability of...
  33. M

    Calculating Electric Force: 2 Electrons & a Proton

    Homework Statement Take a look at this image first If two electrons are each 2.50×10−10 from a proton, as shown in the figure, find the magnitude and of the net electrical force they will exert on the proton. Homework Equations The Attempt at a Solution k=1/4πε0 So what...
  34. X

    Maximum unpaired electrons in an atom

    Homework Statement If there are 13 electrons in M shell and one electron in N shell, the the number of unpaired electrons in such atom will be Homework Equations M- shell N- shell The Attempt at a Solution The configuration should be 3s2 3p6 3d5 4s1 hence the answer should be 6
  35. dexterdev

    Can we give an analogy for nucleus to sun and electrons to planets

    Can we give an analogy for nucleus to sun and electrons to planets...... Hi all, Can we give an analogy for nucleus to sun and electrons to planets...... like this in several galaxies... and galaxies together form some other material in larger scale. Also can we say wave nature of...
  36. S

    Need explanation on how electrons and electricity work

    Hey guys I'm a new member and I will be mostly asking questions :P Anyways ... Physics subjects in my school are about electricity now and my teachers aren't very good, so I can't clearly understand what they're saying. To get to the bottom line, our lesson was about electrons and...
  37. Islam Hassan

    Relating Movement of Electrons in Currents to Wire Movement/Energy/Power

    Off the Wikipedia: "...in a copper wire of cross-section 0.5 mm2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second." Suppose we have a setup with a very very light wire which can transmit very very high currents. Once the current is...
  38. D

    How does potential act as a boundary for electrons in infinite well

    Im wondering how potential can act as a boundary for electrons in a 1-D time independent infinite well?
  39. LarryS

    Electrons Entangled with Nucleus?

    Consider the simplest of all possible atoms: A hydrogen atom with only a proton as its nucleus. According to QFT, the electron is constantly exchanging photons with the proton. So, are the electron and proton entangled? Thanks in advance.
  40. S

    Pauli Principle and Electrons in a Metal

    Why must we apply the Pauli Principle to electrons in a metal? Do they share a many-body wavefunction? The saying is that no two electrons may occupy the same state, but am I allowed to say "well, this electron is at the top of the metal, and there is another one at the bottom, those two are...
  41. X

    If each orbital can hold a maximum of 3 electrons

    Homework Statement If each orbital can hold a maximum of 3 electrons, the number of elements in the 4th period of long form of periodic table will be? Homework Equations ? The Attempt at a Solution I am not able to decide from where should I begin?
  42. M

    Acceleration of electrons in lamp

    Homework Statement Hello. I have an exam soon so I need to do many exercises. I have a problem with one. I need to get an acceleration of electrons in lamp which energy is 14 000 eV and magnetic induction is B = 5.5*10^(-5) T. The Attempt at a Solution The correct result is...
  43. X

    Kinetic energy of the emitted electrons

    Homework Statement When the frequency of light incident on a metallic plate is doubled, the K.E. of the emitted photoelectrons will be? Homework Equations The answer should be either doubled or increased but more than double of the previous kinetic energy The Attempt at a Solution λ=...
  44. A

    Do free electrons protons neutrons assemble into atoms?

    Dear Physics Forum, I wanted to know if there is any theory of elementary particles that explains why protons, neutrons, and electrons assemble into atoms? When these particles were first made in the Universe, why do the assemble into atoms? For example, why don't electrons simply bind...
  45. C

    Electrons - Relativistic velocity addition

    electrons -- Relativistic velocity addition... Homework Statement an observer measures the velocity of two electrons, finding one with a speed c/2 in the x direction and the other c/2 in the y direction. what is the relative speed of the two electrons. Homework Equations The...
  46. E

    Exploring the 'Legal' Discrete Energy of Electrons in Atoms

    Couldn't decide where to post... Chemistry or quantum mechanics... But posted here cause I wanted to know a physicist's view... We know that the electrons in the atom have discrete energy,I mean not just any energy... An electron can't have the energy between 2s and 2p orbitals... But after...
  47. N

    Work done by moving electrons through electric potential?

    Homework Statement A parallel-plate capacitor is charged to an electric potential of 100 V by moving 4x10^19 electrons from one plate to the other. How much work was done? Homework Equations How much work was done? The Attempt at a Solution Work is then simply equals to...
  48. N

    Electrons in Nucleus: What Prevents Collision?

    What prevents the electrons from hitting the nucleus? Shouldn't the proton attract it and destroy the atom?
  49. fluidistic

    Number of electrons in the conduction band of various metals

    Homework Statement Calculate the number n_0 of electrons per volume unit in the conduction band for the lithium, copper and aluminium. Compare this result with the number of electrons of valence per volume unit of these metals. Homework Equations None given, no ressource either...
  50. C

    Free electrons at zero kelvin?

    At zero kelvin,are there free electrons? At zero kelvin,the free electrons should have ZERO energy.But they are able to move under the influence of a electric field? But when they are attracted towards the positive potential shouldn't they gain K.E? So they are moving at zero kelvin?
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