Showing posts with label who discovered electron microscope. Show all posts
Showing posts with label who discovered electron microscope. Show all posts

Friday, 8 March 2019

What experts are saying about electrons||Electron configuration

One of the building blocks, which is there in you, in me and in every particle of any matter you will find all over the universe, the electron is a negatively charged particle.what is electron transport chain? what is electron beam machining?

 To figure out such questions, you can go on reading till the end, I am gonna talk about what experts are saying about electrons and electronic configuration


What experts are saying about electrons || Electron configuration

The electron is a subatomic particle along with proton and neutron, it revolves around the nucleus in different orbits which represents different energy level, the higher the distance from nucleus the better the energy possessed by the electron

the electron is responsible for current flowing in conductors, in fact, electric current is nothing but the flow of free electron. within conductors, electron flows freely from atom to atom

current flows generally from negative pole to positive pole, although in curriculum direction of current flow is taken as positive to the negative pole.


JJ Thompson was the discoverer of the electron, despite all the experiments he performed on electron he could only manage to find its charge to mass ratio, the credit of finding the charge of electron goes to Robert Millikan through oil drop experiment in 1909.

A charge of the electron is called elementary charge value of which is 1.602 × 10-19 coulomb but due to its negative charge, a value is given by -1.602 × 10-19 coulomb 

The charge of a proton is also equal to elementary charge in spite of its more massiness than an electron, so in neutral atoms, there are as many numbers of electrons as the proton.

in some natural unit systems, such as a system of atomic units, e functions as a unit of electric charge, that is e is equal to 1 unit in those systems, use of an elementary charge as a unit was promoted by George Stoney in 1874 for the first system of natural units

at that time the particle which we call was not discovered since then the difference between particle electron and charge of the electron is still blurred.


The electron configuration of atomic species allows us to understand the shape and energy of its electrons,
many rules are referred to understand configuration and location of electron its prospective energy state


however these assignments are arbitrary and it is always uncertain as to which electron is being described, understanding configuration gives a good idea about bonding, magnetism and other chemical properties

an electron is able to move from one energy level to another by either absorbing or by radiating light particle known as a photon, knowledge of an electronic configuration is important in the understanding of a periodic table

shells and subshells are first conceived through the Bohr model, now at present despite being understanding in terms of quantum mechanic nature of the electron, a configuration is still understood by shell and subshell

shell is a set of allowed state, which shares the same main quantum number n, now nth shell can occupy maximum  2n2 .meaning fist shell can occupy 2, second can 8

the factor of 2 arises because the number of states allowed is doubled due to electron spin, each atomic orbital can admit up to two electron one with +1\2 spin and other with -1\2 spin

a subshell is a set of states defined by common azimuthal quantum number l, within a shell the values l= 0, 1, 2, 3 corresponds to s,p,d,f labels, the max number of an electron that can be added in orbital is given by 2(2l + 1).

the energy associated with orbital is considered the energy of an electron, thus total energy of an atom is the addition of energy of each electron

the configuration which corresponds to the lowest energy is called ground state any other state is called excited state. the excitation of valence electrons(outer most orbital electrons) need energy corresponds to the photon

and excitation of core electron needs relatively higher energy.


Electron velocity can also be termed as a drift velocity, is the average velocity attained by charged particles, due to the presence of an electric field, in general electrons in conductor roams randomly at the Fermi velocity

so the net flow of electron is zero, adding an electric field will result into a small net flow in one direction which is called drift, drift velocity is directly proportional to current and in resistive material, it is also proportional to the field

the Ohm's law can be expressed in terms of drift velocity 
u=\mu E,

where u is a drift velocity and mu is electron mobility, E is an electric field


An electron microscope uses an accelerated electron as a source of illumination, the wavelengths of an electron are up to 100,000 times more than light, hence electron microscope have higher resolution than an optical microscope


a scanning transmission type of microscope has achieved 50 pm resolution, and magnification up to 10,000,000 x, whereas normal ones are limited to 200 nm and magnifications below 2000 x.

in 1926 harsh Busch developed an electromagnetic lens, the physicist Leo Szilard tried in 1928 to convince him to build microscope so he applied for a patent, the prototype electron microscope capable of four hundred power magnification was developed by Ernst Ruska in 1931.

in the May of the same year, Reinhold Fudenberg obtained a patent for electron microscope Ernst lube built and obtained images from the prototype, applied a concept used in Gutenberg's patent

in the following year, 1933 Ruska built the first electron microscope that exceeded the resolution of an optical microscope.


Electron beam machining is like laser beam machining, a difference is instead of a laser electron beam is used to the incident on workpiece.result is the generation of heat and melting with vaporization of the workpiece

this process takes place inside the vacuum chamber


It works on the principle of conversion of kinetic energy into heat energy, when the high-speed electron collides with workpiece it transfers its kinetic energy to heat energy which ultimately vaporizes piece

here the reason vacuum used is, if there are air particles electrons will collide before reaching a target and loose energy



1.ELECTRON GUN - It is used to launch electron and to target them at small spot, it is generally kathode ray tube, which also accelerates them at proper velocity, usually tungsten is used to make it, then it is used to heat up 2500 degree centigrade, which causes electron to comes out due to gaining energy

2. MAGNETIC LENSES -  Which shapes the electron beam and doesn't allow to deflect electrons, this lenses allow only to pass convergent electron, thus a highly focused beam is obtained,  they also accept the low energy electrons thereby improving the quality of the same

3.WORKPIECE AND HOLDING DEVICE -It can machine both metallic and nonmetallic device, the workpiece is held by a suitable fixture which is mounted on CNC machine, this table can be moved in all direction controlling the shaping of material.

4.ELECTROMAGNETIC LENSE AND DEFLECTION COIL - Electromagnetic beam is used to focus the beam at the spot, so the high-intensity beam reaches the target, deflection coil doesn't allow to deflect electrons thereby increasing its intensity.


The electron tube produces high-velocity electrons which go to anode tube, which is placed after the cathode tube, now this high intense beam passes through magnetic lenses, there are series of lenses which take care of convergent electron passes through it

these electrons pass through an electromagnetic coil and deflection coil it focuses beam at the spot, this high-velocity beam collides with a workpiece and loses its kinetic energy into heat energy

this removes material from the contact surface and whole set up is kept in a vacuum or else electrons lose energy unnecessarily. to know more about this you can visit 


Electron transport chain is a series of complexes that transfer the electron from donors to acceptors through redox reactions and couples this with a transfer of protons

this creates the electrochemical gradient that drives the synthesis of adenosine triphosphate(ATP) which stores energy electrochemically in the form of highly strained bonds

the molecules of the chain peptides, enzymes and others, the final acceptor in the chain of aerobic respiration is molecule oxygen, although the variety of acceptors lie sulfate is there in aerobic respiration


electron transport chain is used in taking out energy from photosynthesis through redox, electron transport chains are major sites of premature electron leakage to oxygen, generating superoxides and potentially escalated oxidative stress

the function of this chain is to produce transmembrane proton electrochemical gradient as a result of redox reactions.if protons flow back through the membrane, they enable mechanical work such as rotating bacterial flagella

most eucaryotic cells have mitochondria which produce ATP from a product of citric acid cycle, fatty acid oxidation, and amino acid oxidation, at the mitochondrial inner membrane, electrons from NADH to FADH2 pass the electron chain to oxygen.

the electron chain comprises of enzymatic series of donors and acceptors, each electron donor will pass electron to the electrogenerative acceptor, which in turn transfer this to another acceptor

the process which continues till it reaches oxygen, a passage of electron between donor and acceptor generates energy, which is used to generate proton gradient.


The etc is important in photosynthesis as the processes that maintain electrochemical gradient used to drive ATP and NADPH synthesis by moving protons from the chloroplast stroma across the thylakoid membrane into the thylakoid lumen

Producing ATP - in mitochondria, electron transport chains pump H plus ions through a membrane, which produces a concentration gradient this process also happens in chloroplasts

Producing NADPH - While one electron chain provides energy used to make ATP, a second electron chain receives an excited electron from chlorophyll molecule and uses them to make NADPH

In photosynthesis the light-dependent reaction takes place on thylakoid membrane the inside of the thylakoid membranes is lumen and the outside the thylakoid is the stroma, where are light independent reactions takes place 


the thylakoid membrane contains some integral membrane protein complexes that catalyze the light reaction there are four major protein complexes, photosystem 2, cytochrome b6f, photosystem 1, and ATP synthase

when a chlorophyl a molecule within a reaction center of ps 2 absorbs a photon, an electron in this molecule attains a higher energy level as this state is very unstable it makes the electron releases energy through redox reaction called ETC.

The electron flows go from PSII TO cytochrome b6f to PSI .in the PSI the electron gets energy from another photon, the final electron acceptor is NADP

Cytochrome b6f and ATP synthase work together to create ATP, the proton gradient across the thylakoid membrane creates proton motive force 

this is used by ATP synthase to form ATP, in cyclic photophosphorylation, cytochrome b6f uses the energy of electron from not only PSII but also PSI to create more ATP

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