Presentation on theme: "The structure of the atom"— Presentation transcript:
1The structure of the atom Chapter 3.2The structure of the atom
2ObjectivesSummarize 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.
3Structure 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
5Discovery 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
6Discovery 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
7Composition 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