Presentation on theme: "The structure of the atom"— Presentation transcript:
1 The structure of the atom Chapter 3.2The structure of the atom
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.Nucleusvery small region located at the center of an atomContainsProtons – positive charged particleNeutron – particle with NO chargeArea surrounding nucleusElectron cloudElectrons – negative charged particleSubatomic particlesVisual Concept – Click Here
5 Discovery of the Electron Late 1800’s – J.J. Thomson discovered the electron through experiments with cathode- ray tubes.Plum Pudding Model of atomRobert A. Millikan – 1909 – Oil drop experimentElectron is 1/1837 the mass of hydrogen atomVisual Concept 1 – Click HereVisual Concept 2 – Click Here
6 Discovery of the Atomic Nucleus In 1911 – Ernest Rutherford – Gold Foil ExperimentShowed that there was a small – dense positively charged nucleus of an atom.Visual Concept – Click Here
7 Composition of the Atomic Nucleus All atomic nuclei are made of protons and neutrons.Atoms are electrically neutral - contain equal numbers of protons and electronsNuclear Forces – Short range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles togetherSizes of AtomsNucleus compared to rest of atom - approximately size of marble compared to a large football stadium.Atom is mostly empty space