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Atomic structure power point1/12/2024 Thomson Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.Įrnest Rutherford’sGold Foil Experiment - 1911 1932 – James Chadwick confirmed the existence of the “neutron” – a particle with no charge, but a mass nearly equal to a proton.Eugen Goldstein in 1886 observed what is now called the “proton” - particles with a positive charge, and a relative mass of 1 (or 1840 times that of an electron).Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons Electrons have so little mass that atoms must contain other particles that account for most of the massĬonclusions from the Study of the Electron: All elements must contain identically charged electrons. Mass of the Electron Mass of the electron is 9.11 x 10-28 g The oil drop apparatus 1916 – Robert Millikan determines the mass of the electron: 1/1840 the mass of a hydrogen atom has one unit of negative chargeĬonclusions from the Study of the Electron: Cathode rays have identical properties regardless of the element used to produce them. Cathode ray tubes pass electricity through a gas that is contained at a very low pressure. Modern Cathode Ray Tubes Television Computer Monitor Thomson used a cathode ray tube to deduce the presence of a negatively charged particle: the electron There are many other types of particles, but we will study these threeĭiscovery of the Electron In 1897, J.J. Electrons, protons, and neutrons are examples of these fundamental particles.One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles:.Describe the structure of atoms, according to the Rutherford atomic model.Identify three types of subatomic particles.Despite their small size, individual atoms are observable with instruments such as scanning tunneling (electron) microscopes.If you could line up 100,000,000 copper atoms in a single file, they would be approximately 1 cm long.Elements are able to be subdivided into smaller and smaller particles – these are the atoms, and they still have properties of that element.John Dalton (1766 – 1844) Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element. Atoms of any one element are different from those of any other element. His ideas did agree with later scientific theory, but did not explain chemical behavior, and was not based on the scientific method – but just philosophyĭalton’s Atomic Theory (experiment based!) All elements are composed of tiny indivisible particles called atoms Atoms of the same element are identical.He believed that atoms were indivisibleand indestructible. – 370 B.C.) was among the first to suggest the existence of atoms (from the Greek word “atomos”)
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