atomic theory defining the atom an atom is the smallest particle of an element that retains its...
TRANSCRIPT
Defining the Atom
An atom is the smallest particle of an element that retains its identity in a reaction.
The basic building blocks of matter that make-up everyday objects.
About a million atoms stacked on top of each other = the thickness of a sheet of paper.
Copyright © 2010 Ryan P. Murphy
Video Link! The size of atomshttp://www.youtube.com/watch?v=yQP4UJh
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Copyright © 2010 Ryan P. Murphy
DemoCritus
Early Greek Scholar-was the first to suggest the existence of atoms
He believed that atoms were indivisible and indestructible.
Never developed a theory lacked experimental support
John Dalton’s Atomic Theories-All matter is composed of tiny indestructible particles called atoms.-Atoms cannot be made or destroyed.-All atoms of the same element are identical.-Different elements have different types of atoms.-Chemical reactions occur when atoms are rearranged.-Atoms of different elements can mix together to form compounds.
Dalton’s Theory Revised
Most of Dalton’s theory is still accepted today EXCEPT that atoms are known to be divisible.
Atoms can be broken down into 3 subatomic particles: electrons, protons and neutrons.
J.J. Thomson
Used a cathode ray tube to prove the smallest particles present must have a negative charge.
http://www.youtube.com/watch?v=RW_zfKOU9uM&feature=related
What did this study find?J.J. Thompson discovered the ELECTRON!!!
Copyright © 2010 Ryan P. Murphy
+
-
J.J. Thomson
Atoms were electrically neutral, so there must be a + particle to cancel out the – charge from the electron.
Developed the Plum Pudding Model (positive ball containing scattered electrons)
Ernest Rutherford
Former student of Thomson, DISPROVED the Plum Pudding Model of the atom.
The Gold Foil Experiment: Sent a beam of + charges (alpha particles) through a piece of very thin gold foil.
Angles of deflection were measured.
Rutherford
Results: Most of the alpha particles passed straight through, most of the foil must be regions of “empty” space – not a + sphere like Thomson believed.
+ charges and the atoms mass must be found in the center discovered the nucleus
The Nuclear Atom
In Rutherford’s atomic model, the protons and neutrons are located in the nucleus.
The electrons are distributed around the nucleus and occupy almost all the volume of the atoms.
Video! Rutherford’s Gold Foil Experimenthttp://www.youtube.com/watch?v=5pZj0u_
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Copyright © 2010 Ryan P. Murphy
• Neils Bohr Model (1913): Depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus– .
Copyright © 2010 Ryan P. Murphy
– He asks the clerk “How much are the movies?”
Copyright © 2010 Ryan P. Murphy
“For you…”“No
Charge.”
– He asks the clerk “How much are the movies?”
Copyright © 2010 Ryan P. Murphy
“For you…”“No
Charge.”
ATOMIC STRUCTURE
Particle
proton
neutron
electron
Charge
+ ve charge
-ve charge
No charge
1
1
nil
Mass
ATOMIC STRUCTURE
the number of protons in an atom
the number of protons and neutrons in an atom
He2
4 Atomic mass
Atomic number
number of electrons = number of protons
• Review! To find # of protons and electrons– It is the atomic number, or count the P+ or E-.
Copyright © 2010 Ryan P. Murphy
• Review! To find # of protons and electrons– It is the atomic number, or count the P+ or E-.
Copyright © 2010 Ryan P. Murphy
• Review! To find # of protons and electrons– It is the atomic number.– What is this atoms Atomic number?
Copyright © 2010 Ryan P. Murphy
• Review! To find # of neutrons– Subtract the atomic number from the atomic mass to
determine the difference.
Copyright © 2010 Ryan P. Murphy
• Review! To find # of neutrons– Subtract the atomic number from the atomic mass to
determine the difference.– How many neutrons does Lithium have?
Copyright © 2010 Ryan P. Murphy
• Review! To find # of neutrons– Subtract the atomic number from the atomic mass to
determine the difference.– How many neutrons does Lithium have?
Atomic Mass
Copyright © 2010 Ryan P. Murphy
• Review! To find # of neutrons– Subtract the atomic number from the atomic mass to
determine the difference.– How many neutrons does Lithium have?
Atomic Mass
Atomic Number
Copyright © 2010 Ryan P. Murphy
• Review! To find # of neutrons– Subtract the atomic number from the atomic mass to
determine the difference.– How many neutrons does Lithium have?
Atomic Mass
Atomic Number6.94 amu – 3 =
Copyright © 2010 Ryan P. Murphy
• Answer! 6.94 – 3 = 3.94 or 4 neutrons
Atomic Mass
Atomic Number6.94 amu – 3 =
Copyright © 2010 Ryan P. Murphy