Chapter 3.2 : The Structure of the Atom
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This document summarizes key discoveries in atomic structure. It describes J.J. Thomson's discovery of the electron through cathode ray experiments in the late 1800s. It also discusses Ernest Rutherford's gold foil experiment in 1911 that revealed the small, dense, positively charged nucleus at the center of the atom. The properties of subatomic particles like protons, neutrons, and electrons are defined, including their relative charge and mass. The nucleus is shown to be incredibly tiny compared to the overall size of an atom, which is mostly empty space.
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Chapter 3.2 : The Structure of the Atom
- 1. The structure of the atomChapter 3.2
- 2. ObjectivesSummarize the observed properties of cathode rays that led to the discovery of the electron.Summarize the experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus.List the properties of protons, neutrons, and electrons.Define atom.
- 3. Structure of the AtomDefine atom: smallest particle of an element that retains the chemical properties of that element.Subatomic particles:ProtonsNeutronsElectrons
- 4. Discovery of the ElectronLate 1800’s – J.J. Thomson discovered the electron through experiments with cathode-ray tubes.Plum Pudding Model of atomRobert A. Millikan – 1909 – Oil drop experiment
- 5. Electron is 1/1837 the mass of hydrogen atomMillikan’s Oil Drop Experiment
- 6. Discovery of the Atomic NucleusIn 1911 – Ernest Rutherford – Gold Foil ExperimentShowed that there was a small – dense positively charged nucleus of an atom.
- 7. Composition of the Atomic NucleusParticle Relative Charge Mass Number Relative Mass actual massElectron - 1 0 0.0005486 amu 9.109 x 10-31Proton + 1 1 1.007276 amu 1,673 x 10-27Neutron 0 1 1.008665 amu 1,675 x 10-27Nuclear Forces – Short range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together Sizes of Atoms
- 8. Nucleus compared to rest of atom - approximately size of marble compared to a large football stadium.
- 9. Atom is mostly empty spaceWords to live by:David Smillie:Little Willie was a chemist.Little Willie is no more.For what he thought was H2O,Was H2SO4.