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Atomic Theory and Structure. Mr. Lambert Rossview High School. First Things First…. What is an atom?? Smallest particle of an element that retains its identity in a chemical reaction. An atom is an element. What comprises an atom is a non-element. How did we discover the atom?.
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Atomic Theory and Structure Mr. Lambert Rossview High School
First Things First… • What is an atom?? • Smallest particle of an element that retains its identity in a chemical reaction. • An atom is an element. What comprises an atom is a non-element. • How did we discover the atom?
Democritus’s Atomic Philosophy • Suggested the existence of atoms. • Believed, incorrectly, that atoms were indivisible and indestructible. • Why was it incorrect? • Not based on evidence, experiments or scientific method
Dalton’s Atomic Theory • John Dalton • Dalton’s Atomic Theory • All elements are composed of tiny indivisible particles called atoms. • Atoms of the same element are identical. The atoms of any one element are different from those of any other element. • Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds. • Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however are never changed into atoms of another element as a result of a chemical reaction.
Dalton’s Atomic Theory • This graph may help you more fully understand: • Text pg.102
Properties of the Atom • Extremely small • Generally 5x10-11m • Can still be seen through certain microscopes • Scanning Tunneling Microscopes
Pair Share • With the person sitting next to you, ask yourselves these questions: • What is Dalton’s Atomic Theory? • How does an element relate to atoms?
The STRUCTURE OF THE ATOM-Sub-Atomic Particles • Dalton was not completely correct. • Atoms are actually DIVISIBLE. • These smaller particles do not exhibit elemental behavior and are the same in all atoms of all the elements. • Proton, Neutron, Electron
Electrons • e- • Negative charge of 1 • 1/1840 mass of proton • J.J. Thomson • Cathode Ray Tube • Identified negative particle • Robert Millikan • Charge to Mass ratio of e- • # of electrons = # of protons
Protons • p+ • Positive charge of 1 • 1 amu = 1.67 x 10-24 g • Always equals the number of e- • Atomic Number = # of p+
Neutrons • n0 • Neutrally charged particles • Mass equal to that of a proton • # of n0 = amu - protons
So where are they? • Where are sub-atomic particles in an atom? • Atomic Nucleus • Rutherford’s Gold Foil Experiment • Rutherford Atomic Model • Protons and Neutrons in center nucleus • Electrons are distributed around the nucleus. • Nucleus- tiny central core of an atoms and is composed of protons and electrons.
Review Video • www.brightstorm.com/map/134
Homework: • Analytical Comparison of protons, neutrons, electrons, and atomic nuclear theory. • Typed 1 pg response • Read 4.3 in text.