全英化學AtomicStructure課件

1、ATOMIC STRUCTURES.MORRIS 2006HISTORY OF THE ATOM460 BCDemocritus develops the idea of atomshe pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he calledATOMA (greek for indivisible)HISTORY OF THE ATOM1808John Daltonsuggested that all matt

2、er was made up of tiny spheres that were able to bounce around with perfect elasticity and called themATOMS HISTORY OF THE ATOM1898Joseph John Thompsonfound that atoms could sometimes eject a far smaller negative particle which he called anELECTRON HISTORY OF THE ATOMThompson develops the idea that

3、an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electrons charge1904like plums surrounded by pudding.PLUM PUDDINGMODELHISTORY OF THE ATOM1910Ernest Rutherfordoversaw Geiger and Marsden carrying out his famous experim

4、ent. they fired Helium nuclei at a piece of gold foil which was only a few atoms thick.they found that although most of them passed through. About 1 in 10,000 hitHISTORY OF THE ATOMgold foilhelium nucleiThey found that while most of the helium nuclei passed through the foil, a small number were defl

5、ected and, to their surprise, some helium nuclei bounced straight back.helium nucleiHISTORY OF THE ATOMRutherfords new evidence allowed him to propose a more detailed model with a central nucleus. He suggested that the positive charge was all in a central nucleus. With this holding the electrons in

6、place by electrical attractionHowever, this was not the end of the story. HISTORY OF THE ATOM1913Niels Bohrstudied under Rutherford at the Victoria University in Manchester. Bohr refined Rutherfords idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orb

7、it only able to contain a set number of electrons.Bohrs Atomelectrons in orbitsnucleusHELIUM ATOM+NN+-protonelectronneutronShellWhat do these particles consist of?ATOMIC STRUCTUREParticleprotonneutronelectronCharge+ ve charge-ve chargeNo charge11nilMassATOMIC STRUCTUREthe number of protons in an ato

8、mthe number of protons and neutrons in an atomHe24Atomic massAtomic numbernumber of electrons = number of protonsATOMIC STRUCTUREElectrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shella maximum of 2 electrons second shella maximum of 8 electrons third shella maxi

9、mum of 8 electronsATOMIC STRUCTUREThere are two ways to represent the atomic structure of an element or compound;1.Electronic Configuration2.Dot & Cross DiagramsELECTRONIC CONFIGURATIONWith electronic configuration elements are represented numerically by the number of electrons in their shells and n

10、umber of shells. For example;NNitrogen7142 in 1st shell 5 in 2nd shellconfiguration = 2 , 52 + 5 = 7ELECTRONIC CONFIGURATIONWrite the electronic configuration for the following elements;CaOClSiNa2040112381716351428B115a)b)c)d)e)f)2,8,8,22,8,12,8,72,8,42,32,6DOT & CROSS DIAGRAMSWith Dot & Cross diagr

11、ams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example;NitrogenNXXXXXXXN714DOT & CROSS DIAGRAMSDraw the Dot & Cross diagrams for the following elements;OCl8171635a)b)OXXXXXXXXClXXXXXXXXXXXXXXXXXXSUMMARY The Atomic Number of an atom = number of protons in the nucleus. The Atomic Mass of an atom = numb