The structure of the atom

The structure of the atomChapter 3.2ObjectivesSummarize 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.Structure of the AtomDefine atom: smallest particle of an element that retains the chemical properties of that element.Nucleus very small region located at the center of an atomContains Protons positive charged particleNeutron particle with NO chargeArea surrounding nucleusElectron cloudElectrons negative charged particleSubatomic particles

Visual Concept Click HereProperties of subatomic particles

Discovery of the ElectronLate 1800s J.J. Thomson discovered the electron through experiments with cathode-ray tubes.

Robert A. Millikan 1909 Oil drop experimentElectron is 1/1837 the mass of hydrogen atom

Plum Pudding Model of atom

Visual Concept 2 Click HereVisual Concept 1 Click HereDiscovery of the Atomic NucleusIn 1911 Ernest Rutherford Gold Foil ExperimentShowed that there was a small dense positively charged nucleus of an atom.

Visual Concept Click HereComposition of the Atomic NucleusNuclear Forces Short range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together Sizes of AtomsNucleus compared to rest of atom - approximately size of marble compared to a large football stadium.Atom is mostly empty space

All atomic nuclei are made of protons and neutrons.Atoms are electrically neutral - contain equal numbers of protons and electrons