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Discovery of Electron Proton Neutron





The Greek philosopher Democrtius purposed that all matter consists of small indivisible particles which are called as atomos i.e. un-cuttable or indivisible.  
However by the end of 19th century, it was discovered that atoms consist of three fundamental sub-atomic particles; electrons, protons and neutrons.

Out of these sub-atomic particles; electrons were first discovered by Sir John Joseph Thomson (J.J. Thomson) in 1897 on the basis of study of cathode rays by Micheal Faraday in 1832. 
He observed that when electricity was passed through an electrolyte, it gets decomposed into elementary substances and this decomposition is called as electrolysis.

Further the same concept was used by Julius plucker in 1859 during the experiments with gas discharge tube. 
Later in 1870, Sir William Crookes, the English chemist and physicist developed the first cathode ray tube with a high vacuum. It was a long glass tube with metal electrodes on either ends and connected to a vacuum pump for controlling the pressure of gas inside the tube. 
  
At 1 atm pressure, there were no electric current flows through the tube. 
As the pressure reduced to 0.01 atm and a potential difference of about 10000 volts was applied to the electrodes, an electric current flows and light was emitted by the gas. 
This observation proved that some radiations are emitted from cathode and called as cathode rays.

Since these rays flow from cathode to anode, therefore they must have negative charge. 
Cathode rays travel in straight line from cathode to anode and consist of material particles as the wheel placed in the path of rays starts rotating. 
These particles were named as electrons by J.J. Thomson.  
He determined the charge by mass ratio of electrons by deflection of cathode rays under the simultaneous application of electric and magnetic field.

The value of e/m ratio was found to be 1.758820 x 108 Cg-1
This charge by mass ratio for the cathode ray particles was found to be exactly same not taking into account the nature of cathode or the nature of gas taken inside the discharge tube, and eventually showing that the electrons are the basic constituent of all  atoms. 
                                            
In 1886, Eugen Goldstein discovered the existence of a new type of rays in discharge tube and named as anode rays or canal rays. 
He observed these rays behind cathode on passing the electric discharge at low pressure.

Canal or anode rays also travel in straight line and are deflected by electric field towards cathode which proves that they are composed of positively charged particles. 
The charge by mass ratio of these particles depends upon nature of gas taken in discharge tube.

 It observed that the e/m ratio is least with hydrogen gas in discharge tube that is 9.58 x 104 cg-1.  
These lightest positively charged particles were named and characterised as protons by Ernest Rutherford in 1919 who purposed Rutherford model for atom to explain the atomic structure. 
This model proved that the mass of atom is concentrated in nucleus which contains protons. 
But there is one more particle in nucleus named as neutron by James Chadwick in 1932. 
He observed these particles during the bombardment of alpha particles on a thin film of Beryllium as highly penetrating neutral particles.

4Be9 + 2He4  --> 6C12 + 0n1

Some other Sub- Atomic Particles:
Neutrino were discovered in 1927 and it was pauli postulated a particle having zero mass and zero charge. 
Fermi then named it as neutrino but it was around 9n 1952, Allen and Rodeback successfully demonstrated the fee existence of neutrino.

Anti-Neutrino were discovered by Fermi and he indicated that these actually exist and was identified to have identical properties of neutrino but with a oppsite spin and according to fermi neutron decays to form 0n1 ---> 1H1 + -1e0 + neutrino / anitneutrino

Anti-Proton were discovered by Segre in 1955 at University of California produced this particle by bombarding copper target with accelerated protons. 
This particles mass and spin are exactly identicle with proton but the only difference that this particle has is its charge which is -1.

Anti-Electron or in other words the positron were discovered in 1932 by Anderson, a physicists and he found that the bombardment of Boron with an alpha particle resulted in the emission of this particle.

 Cork in 1956 discovered the anti-neutron and he found all the properties are identical to neutron with the exception of its spin which found to be neutron. 
These are produced when a proton strikes an anitproton which results in the production of the neutron and its anti particle antineutron.

Mesons are sub atomic particle having mass in-between to that of an electron and proton. 
These are agin of two different types namely π-meson and μ-mesons
These are also termed as pions and muons respectively.

Pions have mass compared to electron of 273 times and the charge could be negative or positive.

Muons in comparison to electron have mass 207 times and the charge could be either negative or positive.

The last of the mesons are termed as K-mesons and are almost 970 times that of electron in mass number and have a charge of either negative, positive or even zero.

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From Encyclopedia

proton

proton elementary particle having a single positive electrical charge and constituting the nucleus of the ordinary hydrogen atom. The positive charge of the nucleus of any atom is due to its protons. Every atomic nucleus contains one or more protons; the number of protons, called the atomic number, is different for every element (see periodic table ). The mass of the proton is about 1,840 times the mass of the electron and slightly less than the mass of the neutron . The total number of nucleons, as protons and neutrons are collectively called, in any nucleus is the mass number of the nucleus. The existence of the nucleus was postulated by Ernest Rutherford in 1911 to explain his experiments on the scattering of alpha particles; in 1919 he discovered the proton as a product of the disintegration of the atomic nucleus. The proton and the neutron are regarded as two aspects or states of a single entity, the nucleon. The proton is the lightest of the baryon class of elementary particles . The proton and other baryons are composed of triplets of the elementary particle called the quark. A proton, for instance, consists of two quarks called up and one quark called down, a neutron consists of two down quarks and an up quark. The antiparticle of the proton, the antiproton, was discovered in 1955; it has the same mass as the proton but a unit negative charge and opposite magnetic moment. Protons are frequently used in a particle accelerator as either the bombarding (accelerated) particle, the target nucleus, or both. The possibility that the proton may have a finite lifetime has recently come under examination. If the proton does indeed decay into lighter products, however, it takes an extremely long time to do so; experimental evidence suggests that the proton has a lifetime of at least 10 31 years.


From Yahoo Answers

Question:1 draw one atom of this element (element is potassium) atomic number 19 and mass is 39 i got protons - 19 neutrons-20 electrons - 18 how would i draw the atom of the element 2 this atom forms an ion with a charge of 1+. draw a picture represent an ion of this element. how would i draw this picture

Answers:question 1 is looking for potassium in the neutral state. So it has 19 electrons and 19 protons, along with the 20 neutrons. Question 2 is about charged potassium ions. Since it has a charge of +1, you know it has ONE LESS electron in the ionic state -- there's your 18 electrons.

Question:seperately like: proton mass= neutron mass = electron mass=

Answers:proton mass = 1.67262 x 10^-24 g neutron = 1.67493 x 10^-24 g electron = 9.10939 x 10^-28 g

Question:Ok, first off, this is for biology class...not chemistry...which is kind of weird to begin with (I thought it fit better in the chem category). I have to create a 3-D Bohr model of the atom carbon. One of the requirements is that protons, neutrons, and electrons are proportional. I thought that electrons were just a cloud/shells anyway, but I guess not according to this teacher...should I make the protons, neutrons, and electrons the same size, or different sizes? I have only seen them the same size...but I am only in high school...btw, this teacher is really...*cough* annoying, unreliable, confusing, dyslexic (no offense...) *cough* so I have trouble with her instructions sometimes...if they are the same size, please just say so. If not, say what sizes they should be, please! Thanks. (Sorry about the lengthy details.)

Answers:Well done! Electrons do indeed spread out to what quantum physicists call a 'probability cloud' so drawing one seems silly. Electrons aren't like little moons orbiting a planet so you're ahead of your teacher from the sound of it. They're far tinier than protons and neutrons which form the nucleus of an atom. I think electrons are about a 1000th of the size of a proton, I'd have to refresh my memory. Apparently electrons are too small to measure but the proton has one thousand, eight hundred and thirty six times the mass of the electron - I guess you could assume it was that much bigger... Tell her its silly to draw a picture of something that is smaller than the wavelength of light. That'll shut her up. http://en.wikipedia.org/wiki/Atom If you're actually interested in this stuff I recommend you look up a copy of 'in search of schrodinger's cat' which I promise you will enjoy. Kind regards

Question:numbers of protons and neutrons with the resulting ionic charge 1.47 protons, 46 electrons 2.17 protons, 18 electrons 3.16 protons, 18 electrons 4.12 protons, 10 electrons 5.7 protons, 10 electrons

Answers:Can you do math with signed numbers??? Protons have a +1 charge, and electrons have a -1 charge +47 + (-46) = +1 +17 + (-18) = -1 Get the idea? This has nothing to do with neutrons, by the way.

From Youtube

Discovery Of Neutrons :Check us out at www.tutorvista.com The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton. They are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a nucleus is the atomic number and defines the type of element the atom forms. The number of neutrons is the neutron number and determines the isotope of an element. For example, the abundant carbon-12 isotope has 6 protons and 6 neutrons, while the very rare radioactive carbon-14 isotope has 6 protons and 8 neutrons. While bound neutrons in stable nuclei are stable, free neutrons are unstable; they undergo beta decay with a mean lifetime of just under 15 minutes (885.7 0.8 s). Free neutrons are produced in nuclear fission and fusion. Dedicated neutron sources like research reactors and spallation sources produce free neutrons for use in irradiation and in neutron scattering experiments. Even though it is not a chemical element, the free neutron is sometimes included in tables of nuclides. It is then considered to have an atomic number of zero and a mass number of one, and is sometimes referred to as neutronium. In 1931 Walther Bothe and Herbert Becker in Germany found that if the very energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium, boron, or lithium, an unusually penetrating radiation was ...

Protons, neutrons and electrons :Fundamental particles part 1. Explaining the ideas of proton number, nucleon number and isotopes.