Chemistry ProjeCtWorkPrepared by – Shubham ShuklaXI - A
HISTORY OF THE ATOMHISTORY OF THE ATOM460 BC Democritus develops the idea of atomshe pounded up materials in his pestle andmortar until he had reduced them to smallerand smaller particles which he calledATOMAATOMA(greek for indivisible)
HISTORY OF THE ATOMHISTORY OF THE ATOM1808 John Daltonsuggested that all matter was made up oftiny spheres that were able to bounce aroundwith perfect elasticity and called themATOMSATOMS
HISTORY OF THE ATOMHISTORY OF THE ATOM1898 Joseph John Thompsonfound that atoms could sometimes eject afar smaller negative particle which he calledanELECTRONELECTRON
HISTORY OF THE ATOMHISTORY OF THE ATOMThompson develops the idea that an atom was made up ofelectrons scattered unevenly within an elastic sphere surroundedby a soup of positive charge to balance the electrons charge1904like plums surrounded by pudding.PLUM PUDDINGMODEL
HISTORY OF THE ATOMHISTORY OF THE ATOM1910 Ernest Rutherfordoversaw Geiger and Marsden carrying out hisfamous experiment.they fired Helium nuclei at a piece of gold foilwhich was only a few atoms thick.they found that although most of thempassed through. About 1 in 10,000 hit
HISTORY OF THE ATOMHISTORY OF THE ATOMgold foilhelium nucleiThey found that while most of the helium nuclei passedthrough the foil, a small number were deflected and, to theirsurprise, some helium nuclei bounced straight back.helium nuclei
HISTORY OF THE ATOMHISTORY OF THE ATOMRutherford’s new evidence allowed him to propose a moredetailed model with a central nucleus.He suggested that the positive charge was all in a centralnucleus. With this holding the electrons in place by electricalattractionHowever, this was not the end of the story.
HISTORY OF THE ATOMHISTORY OF THE ATOM1913 Niels Bohrstudied under Rutherford at the VictoriaUniversity in Manchester.Bohr refined Rutherfords idea by addingthat the electrons were in orbits. Ratherlike planets orbiting the sun. With eachorbit only able to contain a set number ofelectrons.
HELIUM ATOM+NN+--protonelectron neutronShellWhat do these particles consist of?
ATOMIC STRUCTUREATOMIC STRUCTUREParticleprotonneutronelectronCharge+ ve charge-ve chargeNo charge11nilMass
ATOMIC STRUCTUREATOMIC STRUCTUREthe number of protons in an atomthe number of protons andneutrons in an atomHeHe2244 Atomic massAtomic numbernumber of electrons = number of protons
ATOMIC STRUCTUREATOMIC STRUCTUREElectrons are arranged in Energy Levels orShells around the nucleus of an atom.• first shell a maximum of 2 electrons• second shell a maximum of 8 electrons• third shell a maximum of 8 electrons
ATOMIC STRUCTUREATOMIC STRUCTUREThere are two ways to represent the atomicstructure of an element or compound;1. Electronic Configuration2. Dot & Cross Diagrams
ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATIONWith electronic configuration elements are representednumerically by the number of electrons in their shellsand number of shells. For example;NNitrogen7142 in 1stshell5 in 2ndshellconfiguration = 2 , 52 + 5 = 7
ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATIONWrite the electronic configuration for the followingelements;Ca OCl SiNa2040112381716351428B 115a) b) c)d) e) f)2,8,8,2 2,8,12,8,7 2,8,4 2,32,6
DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMSWith Dot & Cross diagrams elements and compoundsare represented by Dots or Crosses to show electrons,and circles to show the shells. For example;Nitrogen N XX XXXXXN714
DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMSDraw the Dot & Cross diagrams for the followingelements;O Cl8 1716 35a) b)OXXXXXXXXClXXXX XXXXXXXXXXXXXX
SUMMARYSUMMARY1. The Atomic Number of an atom = number ofprotons in the nucleus.2. The Atomic Mass of an atom = number ofProtons + Neutrons in the nucleus.3. The number of Protons = Number of Electrons.4. Electrons orbit the nucleus in shells.5. Each shell can only carry a set number of electrons.
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