User talk:Gilbert Knight

Atomic Structure
--Gilbert Knight (talk) 17:20, 14 October 2017 (UTC)

The idea that we are all made up of tiny 'indivisible' particles know as atoms, has in fact been around since the 5th century B.C. The theory was first introduced by the Greek philosopher Democritus of Abdera. The first 'proper' theory of the atom was put forth by a chemist named John Dalton in the year 1811. In the year 1897, a physicist named JJ Thomson discovered that atoms were in truth not indivisible. He had managed to take particles out of an atom, which had a negative electric charge. These particles were named electrons. The most popular theory of the atom in the early 20th century was the so called 'Plum Pudding Model'. The Plum Pudding Model was the idea that an atom was filled with positive electricity, and that the electrons were like plums in plum pudding and were embedded within the positive electricity. Another physicist named Ernest Rutherford- who also discovered the three types of radioactive decay- was the one to prove this theory wrong. He beamed a ray of alpha particles (the nuclei of a Helium atom) at a sheet of gold foil. To his surprise most of the alpha particles went through the gold foil, but every now and then, an alpha particle was repelled and came straight back the way it came. Because of this, Ernest Rutherford realised that all the positive electricity of the atom was concentrated at the centre, and the electrons hovered around the centre (nucleus) in a cloud. The nucleus of an atom had positive electricity, and hence when the alpha particles came in contact with the nucleus, it would be repelled. Other than that, all the alpha particles would pass right through. Later Ernest Rutherford went on to prove that alpha particles were the nuclei of a helium atom. Today, we know even more than this. Now we know that the nucleus is made of protons- with positive electricity- and neutrons- with no electric charge. We even know that the protons and neutrons are made of another type of particle called quarks. There are six 'flavours' of quarks: up, down, strange, charm, top and bottom. Most particles that are composed of quarks are composed of up and down quarks. Quarks have fractional electric charges. A down quark has a charge of -1/3 and an up quark has a charge of +2/3. A proton is made of two up quarks and one down quark, and a neutron is made of two down quarks and one up quark. Electrons are fundamental particles, and can't be broken up into anything smaller than what it is. The electron belongs to the lepton family. Other leptons are the tau particle, the muon and their neutrinos. All particles that aren't fundamental are made of quarks. A particle with three quarks is known as a baryon. A particle with a quark and an anti-quark is known as a meson. Protons and neutrons exchange mesons with each other, in order to keep each other together. If it weren't for mesons, the protons would repel each other. Quarks are kept together by the exchange of two bosons (particles with integer spins) called gluons and photons. Photons are the carriers of the electromagnetic spectrum, which is the spectrum of the frequencies of light (from radio-waves to gamma rays). Neutrinos are a very small particle with no electric charge. Neutrinos are so small that neither the weak or strong interaction can act upon them. The weak interaction changes the flavour of quarks (like in beta decay), and the strong interaction is what holds nucleons together.