the structure of the atom. atomic theory summary – the atom is the smallest particle of matter
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 Model1. Electrons move around the nucleus in
circular paths called ORBITS / ENERGY LEVELS
2. Each Orbit / energy level can hold a specific # of electrons (always fill the closest orbit first and work out from the nucleus)
3. 1st – 2, 2nd – 8, 3rd – 8, 4th – 18 (2-8-8-18)
Examples
Mg He
N Ne
Summary of the Three Subatomic Particles
1. The Proton:- located inside the nucleus- is positively charged- symbol is p+
2. The Neutron:- located inside the nucleus- has no charge (neutral)- symbol is no
3. 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
elementMass Number (Atomic Mass)
- the number of protons plus the number of neutrons
- measured in atomic mass units (amu)
Since atoms are neutral (ie. No charge), the number of protons in an atom must equal the number of electrons
SummaryAtomic # = #p+ = #e-
Mass # = #p+ + #no
• Read 179-190 (Ch 5.1 and Ch 5.2)• Questions pg. 186 2, 4, 5, 6
pg. 193 2, 3, 5, 7