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Chapter 17 The Atomic Nature of Matter. Structure of the atom Protons + 1 charge Neutrons + 0 charge Electrons - 1 charge Protons and Neutrons are found.

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Presentation on theme: "Chapter 17 The Atomic Nature of Matter. Structure of the atom Protons + 1 charge Neutrons + 0 charge Electrons - 1 charge Protons and Neutrons are found."— Presentation transcript:

1 Chapter 17 The Atomic Nature of Matter

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3 Structure of the atom Protons + 1 charge Neutrons + 0 charge Electrons - 1 charge Protons and Neutrons are found together in the nucleus of the atom Electrons are found in discrete ‘orbital's’ outside the nucleus

4 Atomic Number = #protons Mass Number = #protons + #neutrons (for an individual atom) An Isotope of an element occurs by adding or subtracting neutrons from that atom Atomic Mass = is the mass average of the naturally occuring isotopes of that element

5 If an atom has more protons than electrons it has a net positive charge. These atoms are called cations If an atom has more electrons than protons it has a net negative charge. These atoms are called anions

6 How big are protons, neutrons, and electrons? It turns out that protons and neutrons are much heavier than electrons. Protons and neutrons weigh 1.67 x grams. Electrons weigh 9.11 x grams. Or put another way, protons and neutrons are 1800 times more massive than electrons. Therefore, most of mass of an atom comes from protons and neutrons.

7 Discovery of Atomic Structure It was discovered in 1911 that most of the atom is empty space. If an atom were the size of a football stadium, the nucleus would be the size of a marble in center field, with electrons orbiting on the edge of the stadium. How was this discovered?

8 Ernest Rutherford

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10 The Rutherford Experiment In this experiment helium nuclei (alpha particles) are beamed at a thin piece of gold foil. Since atoms are mostly empty space, most of the helium nuclei pass through the foil. Occasionally, a helium atom will hit a gold nuclei and deflect it at different angles where it is detected by a fluorescent screen.

11 Columns on the periodic table are called groups. Groups of elements have similar chemical properties:

12 Phases of Matter Solid Liquid Gas Plasma Can you identify examples of each? Solid: Desk, Floor, Textbook Liquid: Water Gas: Air we Breathe Plasma: Fluorescent Lights, Sun


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