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.
Homework Statement
Using Equations (A) and (B) explain how to obtain for e/m from the slope of an I vs. \sqrt{V}/{r} graph. Show how to calculate a value for the Earth's magnetic field BE using the intercept of the graph.Homework Equations
(A) B_H = \frac{8NI \mu_0}{R \sqrt{125}} (B)...
...electrical charge?
i've read them described as both. what i want to try to understand is, is the proton and electron simply an electrical charge, nothing more?
or, are they things in their own right, which have an electrical charge?
to use an analogy. peter can have a cardboard sign...
How do electrons revolve around in molecule bonded by covalent bonds? An electron revolves around one nucleus. But if it is going to be shared by another nucleus(as in covalent bond), then how will the electron revolve? does it go all around both the nucleus? Please explain a little deeply.
the way I am understanding how voltage works is how fast one coulomb is passing a point. so if i push more electrons passed a point, it actually gives it a higher voltage?
that and, if i have a screen with a positive potential across it and an electron stream flowing towards it, would the...
Do single non bonding electrons (i.e. on a free radical) always occupy non hybrid orbitals? For example the methyl radical has trigonal planar molecular geometry so the lone electron must occupy a p orbital. Why doesn't it occupy an sp3 orbital instead?
Homework Statement
How to couple spin angular momenta of four electrons?
2. The attempt at a solution
I've no idea.
I've learned coupling of two angular momenta and Clebsch Gordan coefficient.
But donno how to appy that to this system.
Homework Statement
a) What is the energy of a photon that has a wavelength of 0.10 μm?
b) Through approximately what potential difference must electrons be accelerated so that they will exhibit wave nature in passing through an aperture 0.10 μm in diameter?
The Attempt at a Solution
I've...
hello, to preview chemical bonds must be considered only the electrons in the last sublevel and not the electrons in all the level?
for example my book talking of carbon sp hybridation say that we shouldn't expect it make 4 bounds but only 3, why if the carbon need exactly 4 electron to...
i studied that xrays can be produced when a vacancy created ,by knocking of electrons by other high velocity electrons, is filled by other electrons of outer shell. but can electron knock a electron? in same mass collision as in above just velocity is exchanged. so the orbiting electron will...
I have three questions which I have to put into context, much of which is paraphrased from a book by Kerson Huang.
In QED, the source of the gauge field (is the gauge field different from the vector potential?) is the current and charge density j, ρ. When a particle (electron) couples to...
Homework Statement
"What force keeps the electron from falling into the nucleus of the atom?"Homework Equations
The Attempt at a Solution
I have three hypotheses:
1. Neutrons have a negative charge (although there is not only electron capture but also b+ decay)
2. The electrons in the...
Hey guys,
I have a couple of questions regarding X-rays and how they are produced.
1) Is an X-ray an electromagnetic wave or a photon?
2) Why is it that when the electrons collide with the anode in an x-ray tube, X-rays are emitted and not any other electromagnetic wave/photon?
3) When the...
Homework Statement
A neutral object contains an equal number of positive and negative charges. A particular neutral object contains 7.2e26 electrons. If 9.5e6 electrons are removed, what percentage of the electrons where removed?
Homework Equations
coulomb = 6.24e18 electrons
elentary...
Hey,
In x-ray tubes, how come an increase in the voltage results in an increase in the intensity of the electrons. i.e. the no. of electrons emitted per unit time per unit second.
Thanks.
Feel free to answer any subset. I'm not a science person, so apologies in advance for some of the absurdity.
1. When heat up some piece of matter (e.g., a rock), do the the electrons (of the atoms of which the rock is composed of) start moving faster? If so, then why do we observe temperature...
I've been exposed to two different interpretations of the uncertainty principle.
1) If an electron is in a certain state, a measurement of its position will yield a definite result. However, if after the measurement the electron could be returned to the same state, then a repeated measurement...
"Where" do electrons "go"(?) within a covalent bond
If you take a water molecule (H-O-H) with 2 covalent bonds (imagine, just for now, that this is the only 2 atoms around ;-).
The H’s electron and one of the O’s electrons (within the covalent bond) must be “somewhere”.
They were...
Why don't electrons move only along the surface of orbitals?
Moreover, how do electrons move within orbitals, random movement or do they follow a definite path?
In a p-orbital, does one lobe consist of only one electron?
Why is the p-orbital dumbbell shaped and not spherical?
Homework Statement
I am trying to retake an old course in statistical mechanics but run into integrals that i simply have forgotten how to solve.
Given an denstiry of states such that
f(\epsilon)= \frac{1}{|\epsilon |} for \epsilon_{min} \leq \epsilon < 0 and 0 elsewhere
Using the mean...
Homework Statement
An alien civilization has crossed the galaxy to invade the Earth and enslave humanity, again. Their attacks have been successful so far because their assault troops are equipped with handheld weapons that project beams of charged particles (protons & electrons) at very...
Hi
Thinking of the structure of an atom in terms of spherical harmonics; the mathematics of which is the base of schrodinger's wave equation.
If its possible to make the electrons gather at the antinodes, what are the possible applications/uses of this? (Simply a new area for research? or...
This question is pretty straightforward, but I just can't seem to find the answer..
What is the reason that electrons only exist in shells and never between them?
A hint that was given to me was to "think about quantum energy".
I was thinking because if they wouldn't exist in shells, then...
For a simple network of resistive circuit, we can compute the values of current and voltages right? However, I'm more curious about how each individual component behave. Is it possible to somehow isolate each resistor and compute their values individually (e.g. not having to compute the entire...
When electrons gain enough energy to move out to a higher energy orbit then back to their ground state, why do they release a photon? Also, what exactly is 'electromagnetic' about light?
Homework Statement
A beam of electrons, with kinetic energy of 500eV, enters mid-way into the space between two oppositely charged parallel plates with a potential difference of 100V
Homework Equations
Determine the velocity of the electrons
The Attempt at a Solution
KE=0.5mv^2...
Homework Statement
A wire carries a current of 2.0 A for 1.0 hour. How many electrons pass a point in the wire in this time?
A
1.2 x 10-15
B
7.2 x 103
C
1.3 x 1019
D
4.5 x 1022Homework Equations
Q=I/tThe Attempt at a Solution
Q=2(60)=120
number of electrons= 120/1.60217733 × 10-19= but the...
How do you calculate the maximum number of electrons with principal quantum number:
a) 1
b) 2
There is more, but I list two because I want to learn how to do it. How do you show your work mathematically and what is is the principal quantum number?
Quantum mechanics and electrons...
Can anyone explain according to QM why do electrons move around nucleus...? And how does QM explain electrons' orbit or electron cloud...?...
Energy of electrons...
Okay...sorry for such a long post...please be patient... And help me...here i have a question about the electrons' energy in an atom...in every energy level all the electrons contain same amount of energy...but among different energy levels the amount is different...my...
In trying to understand electricity I thought of the following: If I set up a wire one light year long, stretching out into space ½ a light year out and ½ a light year back, and connected a series of light bulbs all the way around the wire, and then connected a battery (large enough to handle...
Where do the electrons that electromagnetic induction mobilizes come from? If electrons are waves as the double-slit experiment demonstrates, couldn't they be generated just as mechanical and light waves are generated?
Latley, I have been doing some internet surfing on the release of electrons from their obit of an atom. I just have a few questions. What is it called when electrons are released from their orbit? How much energy does it take? What are the diffrent ways electrons can be released?
A question in ExamKrackers asks us why triphenylmethanol is so acidic. Link to the structure below:
http://en.wikipedia.org/wiki/Triphenylmethanol
Explanation:
I'm not seeing how the lone pairs on the Oxygen could donate into any of the rings though. It can't donate those electrons onto the...
Hi all,
I would like to know what is the relation between charge and mass (of electron/proton/neutron). How far their masses involve in force that exists between them ?
It is a bit more logical that no more than two electrons can occupy the same position in space, however the Pauli Exclusion principle also concludes that no state exists with more than two electrons having the same momentum. Even the state of the entire universe.
How is this physically...
Hello,
I am a student in Physics and I have some problems to understand how photons and electrons are studied. Is there the assumption that they occupy a so little space in the "Phase space" that they can be considered has point ? Can we expect that in the real case when they "moove" they are...
Spin orbit coupling accounts for the relative motion of a magnetic moment interacting with an electric field.
Is there a direct coupling of the magnetic moments of, say, the electrons in an atom as well? Does a magnetic field emanate from spin 1/2 particles in general?
Thank you for...
Hello. I used discrete electron multiplier (dynodes) for positive ions detection, and it works fine. Now I want to use it for electrons detection with no changes in mode of connecting power supply (-2 kV on 1st dynode, 0 V on last one) . In the past application I don't use the reflector...
Assume that in an imaginary space there are only two electrons.
Now if we spin one of those around itself, without moving its pivot , what would happen to the other one?(I think it would keep moving normally because if it starts turning around the first electron it means we can have "smaller...
Homework Statement
http://dl.dropbox.com/u/305636/yeephysics.jpg
If that doesn't work, the problem states:
A pair of parallel metal plates, 100mm long and a distance of 20mm apart are set up in an evacuated tube as shown. A potential difference is applied to the plates, creating an...
Hey all, I'm a student curently studying in a Singaporean Junior College (American 12th grade equivalent). I was curious and just thought of the following:
Suppose a system with a electron and a proton nucleus, a hydrogen atom.
From electrostatic force and circular motion equations-
F =...
Greetings,
I know that when an electron in an atom emits or absorbs a photon, what changes is the electrons orbit.
What about free electrons? If an electrons moving freely through space emits or absorbs an electron, what changes about the electron? And what determines what frequency...
Hi all. I understand that a hole is the absence of an electron. I have come across textbooks with instances where they talk about movement of minority carriers, and movement of majority carriers. Since the hole has to be one of them, they are referring to moving holes.
But, how can a hole...
Homework Statement
Two electrons are held 1 nm apart and then released. Assuming them to be classical particles, how fast will they be moving when they are far apart?
Homework Equations
Not sure here really due to the lack of info give in the question. I know the work done would be qV...
Homework Statement
suppose you put 5 electrons into an infinite square well. (a) how do the electrons arrange themselves to achieve the lowest total energy? (explain with help of diagram) (b) give an expression for this energy in terms of electron mass, well width L and planks constant
The...
Hi,
Here is magnetism and it`s effect on electrons question for you eggheads.
I am experimenting with a unusual transformer design, it is a flyback transformer ferrite core (square) with a circular secondary spool filled with wire on the outside, a primary coil in the middle wound...
A plasma is when electrons become unbound by their atoms. So does that mean that you can get a different plasma for all different types of atoms (like gold plasma and helium plasma)?
Also the electrons are not free as they are bound to the plasma (but not individual neuclei) by the magentic...
Homework Statement
A helium atom had two electrons in the first shell (1s). Explain, withour detailed derivation, what the value of the total spin quantum number is.
Homework Equations
?
The Attempt at a Solution
Since the 2 electrons are in the first (1s) shell they must have...