![]() But while most of the particles did pass through, some bounced right back, suggesting that the foil was more like a thick net with a very large mesh. The effect would have been like a bunch of tennis balls punching through a thin paper screen. Under Thompson's model, the atom's thinly dispersed positive charge would not be enough to deflect the particles in any one place. While studying the effects of X-rays on gases, Rutherford decided to investigate atoms more closely by shooting small, positively charged alpha particles at a sheet of gold foil. This was because he happened to have some pretty smart students, including a certain Ernest Rutherford, who would become known as the father of the nuclear age. Thompson won a Nobel Prize in 1906 for his electron discovery, but his model of the atom didn't stick around long. In what we might call the chocolate chip cookie model of the atom, he showed atoms as uniformly packed spheres of positive matter filled with negatively charged electrons. Thompson's 1897 discovery of the electron. Though he received many honors for his work, as a Quaker, Dalton lived modestly until the end of his days.Ītomic theory was now accepted by the scientific community, but the next major advancement would not come until nearly a century later with the physicist J.J. He concluded that the various compounds were combinations of atoms of different elements, each of a particular size and mass that could neither be created nor destroyed. Whereas Democritus's atomism had been purely theoretical, Dalton showed that common substances always broke down into the same elements in the same proportions. Aristotle, for instance, disagreed completely, stating instead that matter was made of four elements: earth, wind, water, and fire, and most later scientists followed suit.Ītoms would remain all but forgotten until 1808 when a Quaker teacher named John Dalton sought to challenge the Aristotelian theory. His ideas were opposed by the more popular philosophers of his day. He called these particles "atomos," Greek for indivisible. And he even speculated that they vary in size and shape depending on the substance they compose. It was around 440 BCE that Democritus first proposed that everything in the world was made up of tiny particles surrounded by empty space. What do an ancient Greek philosopher and a 19th century Quaker have in common with Nobel Prize-winning scientists? Although they are separated over 2,400 years of history, each of them contributed to answering the eternal question: what is stuff made of? Now please watch this brief (5:22) video on the (brief) history of atomic theory. In contrast, most of the volume of the atom is filled with electrons. ![]() Most of the mass of the atom is located in the nucleus, with the mass of the proton roughly equal to the larger neutron, but 1840 times the mass of the electron. ![]() Chemical reactions to move electrons can affect how atoms bind to each other but cannot be used to divide atoms. ![]() In fact, neutrons are required to make the nucleus stable once you have more than one proton in the nucleus.Ītoms are the fundamental building blocks of matter they cannot be divided using chemicals. Neutrons and protons are held in the nucleus by the nuclear force, and neutrons are not simply a proton plus an electron. The protons are positively charged, electrons are negatively charged, and neutrons possess no charge. We now know that the atom has a nucleus composed of protons and neutrons surrounded by clouds of electrons. The word atom is derived from the ancient Greek adjective atomos, meaning "uncuttable" or "indivisible." The earliest concepts of the nature of the atom were debated in ancient India and ancient Greece. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |