8/18/2015
ATOMIC STRUCTURE
I WILL BE ABLE TO DESCRIBE THE ATOMIC STRUCTURE OF AN ATOM.
I WILL BE ABLE TO LIST THE CONTRIBUTIONS VARIOUS SCIENTISTS HAVE MADE
TO DEVELOP AN ACCEPTED MODEL OF THE ATOM.
I WILL BE ABLE TO EXPLAIN THE RELATIONSHIP BETWEEN THE ATOMIC NUMBER
AND THE MASS NUMBER OF AN ELEMENT.
DALTON – SOLID SPHERES
• Did his work in the late 1700s early 1800s
• He said:
• All matter is made up of tiny, indivisible particles called atoms
• All atoms of an element are identical
• Atoms of different elements are different
• Atoms are rearranged to form new substances in chemical
reactions but are never created or destroyed.
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8/18/2015
THOMPSON – ELECTRONS!
• Did his work in the late 1800s
• Using a cathode tube (think electron gun) he was able
to discover that there were negative particles…he
called them electrons
• Electrons were suspended in a positive charge – plum
pudding
RUTHERFORD – NUCLEUS!
• In the early 1900s he aimed tiny positive alpha particles at
gold foil testing Thompson’s model.
• If Thompson was right the alpha particles should pass
straight through. Some did pass straight through but some
were deflected.
• He explained this by saying there is a dense positively
charged nucleus
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8/18/2015
CHADWICK – NEUTRONS!
• After performing experiments in 1932 James Chadwick
confirmed the nuclei contain neutrons and protons.
BOHR – ENERGY LEVELS
• Bohr noticed that when element samples had
electrical/thermal energy applied to them they gave
off different colours of light.
• Electrons orbit at definite energy levels.
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8/18/2015
BOHR – RUTHERFORD DIAGRAMS
• Rules:
• 2 e- in n=1
• 8 e- in n=2
• 18 in n=3
EXAMPLES
• Draw the B-R Diagram for Oxygen & Sodium
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8/18/2015
TODAY’S TASKS
• Read Section 1.2
• Pg. 16 # 1, 2, 5, 10
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