Bellwork: Get out your diagram from your research paper. Get out a sheet of paper to take some notes on. Fill in the Following Table in your notes (assume an atom unless otherwise stated: Symbol Protons Electrons Neutrons Atomic # Mass # 24 Na + 11 11 10 13 11 24 63 Cu 29 29 29 34 29 63
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Bellwork: Get out your diagram from your research paper. Get out a sheet of paper to take some notes on. Fill in the Following Table in your notes (assume an atom unless otherwise stated:
Symbol Protons Electrons Neutrons Atomic # Mass #
24 Na+ 11
11 10 13 11 24
63 Cu 29
29 29 34 29 63
Development of the Atomic Theory
What does the Greek word atomos mean?
• The Greek word “atomos” means not able to be divided
or “indivisible.”
Democritus was an ancient Greek philosopher who lived from 460 - 370 B.C.
What did Democritus conclude about cutting matter in half? There was a limit to how far you could divide matter. You would eventually end up with a piece of matter that could not be cut.
Who was Democritus?
• Aristotle believed that matter could be divided into smaller and smaller pieces forever.
• He held a very strong influence on popular belief and his views on this were accepted for two thousand years.
Why weren’t Democritus’s ideas accepted?
John Dalton 1776-1844 • Two thousand years later
a British chemist and schoolteacher brings back Democritus’s idea of the atom
• He performed many experiments to study how elements join together to form new substances.
Summary for Dalton’s Atomic Theory
Atoms are tiny and indivisible. Atoms can’t be created or destroyed. Atoms of the same element are the identical.
Atoms of different elements are different. Atoms of different elements combine in simple whole-number ratios to form compounds.
Dalton’s Theory
Experimental evidence Scientific Laws
Law of Conservation on Matter You can’t create or destroy atoms. Law of Definite Proportions Same compounds are same ratio by mass. Law of Multiple Proportions
Different compounds with the same elements are whole number multiples of the atoms.
Experiments Scientific Laws Atomic Theory (observations) (Patterns) (Explanations)
John Dalton realized that there must be an atom as
Expert groups: Get together with people who researched the same scientists as you. Discuss what you need to make sure everyone knows about your scientists. Explain his experiment and procedure Discuss his findings and their significance to modern atomic theory Any problems with his ideas
Now you are going to the home groups of the number you were given. It is your job as the EXPERT to make sure everyone understands what your scientists did. You will be held responsible for this material.
Turn in Diagrams, make sure your name is on them.
Discovery of the Electron In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle. http://viewpure.com/IdTxGJjA4Jw
Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.
- classic planetary model in which electrons whirl around the small but dense nucleus: like planets orbiting the Sun
- developed by the Danish physicist Niels Bohr in 1911
- each electron has a certain energy that is determined by it’s path around the nucleus
Erwin Schrodinger (1926 ) Quantum Mechanical Model Like the Bohr model, the quantum mechanical model of the atom restricts the energy of electrons to certain values. Unlike the Bohr model, however, the quantum mechanical model does not involve an exact path the electron takes around the nucleus.
The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus.
If you need more review of the history of atomic theory: https://www.youtube.com/watch?v=NSAgLvKOPLQ Scientists matching game