# The Structure of the Atom

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

The Structure of the Atom

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

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

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)

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 ( )

Examples Mg He N Ne

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-

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)

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

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