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The Structure of the Atom

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Presentation on theme: "The Structure of the Atom"— Presentation transcript:

1 The Structure of the Atom

2 Atomic Theory Summary – the atom is the smallest particle of matter.

3 History of the Atom Cont.
JJ Thomson (1897) – Raison Bun Theory Electrons (negative) distributed in a positive sphere Cathode Ray Tube used to measure the mass of the electron Ernest Rutherford (1911) – discovered that atoms have a positive nucleus Gold Foil Experiment Positive charge due to protons

4 James Chadwick (1932) – within the nucleus there are protons and neutrons (no charge) Niels Bohr – came up with the current model of the atom taught in Grade 9 and 10 Science; - Bohr Rutherford Model (planetary model)

5 Bohr-Rutherford Model
Electrons move around the nucleus in circular paths called ORBITS / ENERGY LEVELS Each Orbit / energy level can hold a specific # of electrons (always fill the closest orbit first and work out from the nucleus) 1st – 2, 2nd – 8, 3rd – 8, 4th – 18 ( )

6 Examples Mg He N Ne

7 Summary of the Three Subatomic Particles
The Proton: - located inside the nucleus - is positively charged - symbol is p+ The Neutron: - has no charge (neutral) - symbol is no The Electron - orbits outside the nucleus - very tiny compared to the proton or neutron - is negatively charged - symbol is e-

8 Other Terms Atomic Number - the number of protons - unique to each atom, use it to identify an element Mass Number (Atomic Mass) - the number of protons plus the number of neutrons - measured in atomic mass units (amu)

9 Since atoms are neutral (ie
Since atoms are neutral (ie. No charge), the number of protons in an atom must equal the number of electrons Summary Atomic # = #p+ = #e- Mass # = #p+ + #no


11 Read (Ch 5.1 and Ch 5.2) Questions pg , 4, 5, 6 pg , 3, 5, 7

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