Geiger and Marsden exeperiment
Answers
Answer:
The Geiger–Marsden experiments (also called the Rutherford gold foil experiment) were a landmark series of experiments by which scientists discovered that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this by measuring how an alpha particle beam is scattered when it strikes a thin metal foil. The experiments were performed between 1908 and 1913 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester.
follow me for follow back..❤
hope it helps...❤
mark me as the brainliest...❤
Answer:
Contemporary theories of atomic structure Edit
The plum pudding model of the atom, as envisioned by Thomson.
The popular theory of atomic structure at the time of Rutherford's experiment was the "plum pudding model". This model was devised by Lord Kelvin and further developed by J. J. Thomson. Thomson was the scientist who discovered the electron, and that it was a component of every atom. Thomson believed the atom was a sphere of positive charge throughout which the electrons were distributed, a bit like raisins in a Christmas pudding. The existence of protons and neutrons was unknown at this time. They knew atoms were very tiny (Rutherford assumed they were in the order of 10−8 m in radius[1]). This model was based entirely on classical (Newtonian) physics; the current accepted model uses quantum mechanics.
Thomson's model was not universally accepted even before Rutherford's experiments. Thomson himself was never able to develop a complete and stable model of his concept. Japanese scientist Hantaro Nagaoka rejected Thomson's model on the grounds that opposing charges cannot penetrate each other.[2] He proposed instead that electrons orbit the positive charge like the rings around Saturn.[3]
Implications of the plum pudding model Edit
An alpha particle is a sub-microscopic, positively charged particle of matter. According to Thomson's model, if an alpha particle were to collide with an atom, it would just fly straight through, its path being deflected by at most a fraction of a degree. At the atomic scale, the concept of "solid matter" is meaningless, so the alpha particle would not bounce off the atom like a marble. It would be affected only by the atom's electric fields, and Thomson's model predicted that the electric fields in an atom are too weak to affect a passing alpha particle much (alpha particles tend to move very fast). Both the negative and positive charges within the Thomson atom are spread out over the atom's entire volume. According to Coulomb's Law, the less concentrated a sphere of electric charge is, the weaker its electric field at its surface will be.[4][5]
Thomson model alpha particle scattering.svg
As a worked example, consider an alpha particle passing tangentially to a Thomson gold atom, where it will experience the electric field at its strongest and thus experience the maximum deflection θ. Since the electrons are very light compared to the alpha particle, their influence can be neglected[6] and the atom can be seen as a heavy sphere of positive charge.
Qn = positive charge of gold atom = 79 e = 1.266×10−17 C
Qα = charge of alpha particle = 2 e = 3.204×10−19 C
r = radius of a gold atom = 1.44×10−10 m
vα = velocity of alpha particle = 1.53×107 m/s
mα = mass of alpha particle = 6.645×10−27 kg
k = Coulomb's constant = 8.998×109 N·m2/C2
Using classical physics, the alpha particle's lateral change in momentum Δp can be approximated using the impulse of force relationship and the Coulomb force expression:
The outcome of the experiments Edit
Left: Had Thomson's model been correct, all the alpha particles should have passed through the foil with minimal scattering.
Right: What Geiger and Marsden observed was that a small fraction of the alpha particles experienced strong deflection.
At Rutherford's behest, Geiger and Marsden performed a series of experiments where they pointed a beam of alpha particles at a thin foil of metal and measured the scattering pattern by using a fluorescent screen. They spotted alpha particles bouncing off the metal foil in all directions, some right back at the source. This should have been impossible according to Thomson's model; the alpha particles should have all gone straight through. Obviously, those particles had encountered an electrostatic force far greater than Thomson's model suggested they would, which in turn implied that the atom's positive charge was concentrated in a much tinier volume than Thomson imagined.[8]
When Geiger and Marsden shot alpha particles at their metal foil, they noticed only a small fraction of the alpha particles were deflected by more than 90°. Most flew straight through the foil. This suggested that those tiny spheres of intense positive charge were separated by vast gulfs of empty space.[8] Most particles passed through the empty space and experienced negligible deviation, while a handful passed close to the nuclei of the atoms and were deflected through large angles.
Rutherford thus rejected Thomson's model of the atom, and instead proposed a model where the atom consisted of mostly empty space, with all of its positive charge concentrated in its center in a very tiny volume, surrounded by a cloud of electrons
Explanation:
hope it will help you
mark me as Braillent