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The Early Models of the Atom

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1 The Early Models of the Atom
I. Structure of the Atom The Early Models of the Atom

2 Laws Law of Conservation of Mass
Law of Definite /Constant Proportion- compounds have a ________ composition. Carbon tetrachloride is always 1 atom carbon per 4 atoms chlorine. They react in specific ratios by mass. Law of Multiple Proportions- When two elements form more than ______compound, the ratios of the masses of the second element that combine with one gram of the first can be ______ to small whole numbers. The ratio of the masses of oxygen in H2O and H2O2 will be a small whole number (“2”).

3 Dalton’s Atomic Theory
Elements are made up of _________ Atoms of each element are _______. Atoms of different elements are different. Compounds are formed when atoms combine. Each compound has a specific _______ and ______ of atom. Chemical reactions are ________ of atoms. Atoms are not _____ or destroyed.

4 Plum Pudding Model J.J. Thomson is credited with the discovery of the electron _______ Experimentation→ e-/m ratio _______ Experimentation→e- Charge

5 Thomson’s Experiment Voltage source - +

6 Thomson’s Experiment Voltage source - +

7 - + Thomson’s Experiment Voltage source
Passing an electric current makes a beam appear to move from the _____ to the _____ end.

8 Thomson’s Experiment Voltage source By adding an electric field

9 Thomson’s Experiment Voltage source + -
By adding an electric field, he found that the moving pieces were __________

10 Thomson’s Model Found the electron.
Couldn’t find positive (for a while). Said the atom was like A bunch of positive stuff, with the ______ able to be removed.

11 Millikan’s Experiment
Atomizer Oil droplets - + Oil Telescope

12 Millikan’s Experiment
X-rays _______ give some electrons a charge.

13 Millikan’s Experiment
Some drops would hover From the m of the drop and the charge on the plates, he calculated the ___________

14 Rutherford’s Experiment
Used to produce alpha particles (+ charged particles). Aimed alpha particles at gold foil by drilling hole in block. Since the mass is evenly distributed in gold atoms alpha particles should go through. Used gold foil because it could be made atoms thin.

15 Florescent Screen Lead block Uranium Gold Foil

16 What he expected

17 Because

18 Because, he thought the mass was evenly distributed in the atom.

19 What he got

20 How he explained it Atom is mostly _____ Small dense, _______ piece at center. Alpha particles are ______ by it if they get close enough. +

21 +

22 Modern View The atom is mostly empty space. ------ regions
Nucleus- protons and neutrons. Electron cloud- region where you might find an

23 The Mass and Change of the Electron, Proton, and Neutron

24 Sub-atomic Particles ___- atomic number = number of protons determines type of atom. ___ - mass number = number of protons + neutrons. __________ = number of electrons if neutral.

25 Symbols A X Z 23 Na 11

26 Niels Bohr Atomic Model
Fixed Orbits, Predictable Paths Derived from Max Planck’s description of light packets or quanta called photons

1924-Louis DeBroglie applied ____________to model 1927-Erwin Schrodinger applied wave equation to model Heinsberg’s Principle said speed and position cannot be calculated at same time

The Atomic Theorists

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