where and when did James Chadwick discover the neutron?

Question

where and when did James Chadwick discover the neutron?

Answer 1

Chadwick discovers the neutron

1932





For four years, James Chadwick was a prisoner of war in Germany. When World War I ended, he returned to his native England to rejoin the mentor of his undergraduate days, Ernest Rutherford. Now head of Cambridge University's nuclear physics lab, Rutherford oversaw Chadwick's PhD in 1921 and then made him assistant director of the lab.



Chadwick's own research focused on radioactivity. In 1919 Rutherford had discovered the proton, a positively charged particle within the atom's nucleus. But they and other researchers were finding that the proton did not seem to be the only particle in the nucleus.



As they studied atomic disintegration, they kept seeing that the atomic number (number of protons in the nucleus, equivalent to the positive charge of the atom) was less than the atomic mass (average mass of the atom). For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus were adding to the mass. One leading explanation was that there were electrons and additional protons in the nucleus as well -- the protons still contributed their mass but their positive charge was canceled out by the negatively charged electrons. So in the helium example, there would be four protons and two electrons in the nucleus to yield a mass of 4 but a charge of only 2. Rutherford also put out the idea that there could be a particle with mass but no charge. He called it a neutron, and imagined it as a paired proton and electron. There was no evidence for any of these ideas.



Chadwick kept the problem in the back of his mind while working on other things. Experiments in Europe caught his eye, especially those of Frederic and Irene Joliot-Curie. They used a different method for tracking particle radiation. Chadwick repeated their experiments but with the goal of looking for a neutral particle -- one with the same mass as a proton, but with zero charge. His experiments were successful. He was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's. He published his findings with characteristic modesty in a first paper entitled "Possible Existence of Neutron." In 1935 he received the Nobel Prize for his discovery.



His findings were quickly accepted and Werner Heisenberg then showed that the neutron could not be a proton-electron pairing, but had to be its own unique particle -- the third piece of the atom to be found. This new idea dramatically changed the picture of the atom and accelerated discoveries in atomic physics. Physicists soon found that the neutron made an ideal "bullet" for bombarding other nuclei. Unlike charged particles, it was not repelled by similarly-charged particles and could smash right into the nucleus. Before long, neutron bombardment was applied to the uranium atom, splitting its nucleus and releasing the huge amounts of energy predicted by Einstein's equation E = mc2.

Answer 2

c

Answer 3

Chadwick discovered in 1932 in University of Cambridge that the particle previously described to be produced from the collision between alpha particles and beryllium atom described by the Curies could produce another particle known as protons .He described the particle produced by the Curies experiment as Neutrons.

Answer 4

in his lab

Answer 5

dont no why? you can goggle it we are in 2006.

Answer 6

After the war Chadwick returned to Cambridge where he worked with Ernest Rutherford in investigating the emission of gamma rays from radioactive materials. They also studied the transmutation of elements by bombarding them with alpha particles, and investigated the nature of the atomic nucleus.



In 1932 Chadwick made a fundamental discovery in the domain of nuclear science: he discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charge. In contrast with the helium nuclei (alpha particles) which are positively charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. In this way, Chadwick prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb. For this epochal discovery he was awarded the Hughes Medal of the Royal Society in 1932, and subsequently the Nobel Prize for Physics in 1935. Later, he found out that a German scientist had discovered the neutron at the same time. But Hans Falkenhagen (Rostock) was afraid of publishing his results. When Chadwick learned of Falkenhagen's discovery, he offered to share the Nobel Prize with him. Falkenhagen, however, modestly refused the honour.



Chadwick’s discovery made it possible to create elements heavier than uranium in the laboratory. His discovery particularly inspired Enrico Fermi, Italian physicist and Nobel laureate, to discover nuclear reactions brought by slowed neutrons, and led Lise Meitner, Austrian physicist, to the discovery of “nuclear fission”, which triggered the development of an atomic bomb.