1. A Brief History of Atomic Theory
This Section will focus on Scientists who have had an impact on the study of the atom.
Ready To Meet Them?

2. Democritus
Democritus proposed that matter cannot be broken down indefinitely. At some point you end up with a piece that can’t be divided. That smallest piece he called an atom, from the Greek word atomos, which means “indivisible”.
B.C.
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3. Democritus’ Model “Atomos”
ATOMOS was the word Democritus used the point, or stage where matter cannot be broken down any further. ATOMOS literally means “indivisible”

4. John Dalton
John Dalton was a British chemist.He was the first modern scientist to propose the existence of atoms.He described an atom as an invisible indestructible, solid sphere, like a billiard ball.

5. Dalton’s Model
The “Indivisible Sphere”

6. Sir Joseph “J.J.” Thomson
J.J. Thomson was a British physicist who was the first scientist to propose the plum pudding model. He was also the first to propose the theory of the negatively charged electron. He was credited for the discovery. He also proposed the isotope.

7. Thomson “plum pudding” model+ -

8. Ernest Rutherford
Ernest Rutherford experiments proved that atoms are mostly empty space Discovered the nuclear, which contains positively charged particles .Was the first to suggest that electrons circle the dense nucleus.

9. Rutherford’s Model
Nucleus
It has a + charge
Electron Negative charge

10. Niels Bohr
Niels Bohr stated that electrons move in different orbits, or energy levels, around the nucleus like planets orbit the sun. Each energy level is located a specific distance from the nucleus and contains a certain number of electrons.
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11. Bohr Model
Nucleus
Energy
levels
Electron-
negative charge

12. Current Model
This model is based upon Bohr’s model, except that electrons orbit the nucleus in random patterns. The region where these particles are found is referred to as the electron cloud.
Electron Clouds
Nucleus
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13. Demitri Mendeleev
Demitri Mendeleev was a Russian scientist. He was the first person to make the periodic table. He also wrote a chemistry book.The periodic table is a tool to help read elements.

14. Mendeleev’s Table

15. Modern Periodic Table

16. How to Read the Table 6 2 C 4 carbon 12.01115 Atomic Number C
carbon
Chemical Symbol
Number of Electrons in each energy field
Element Name
Atomic Mass

17. Calculating Atomic Mass6 C
Carbon
To find the Atomic Mass, you look at the bottom number in the Atom tile and round it to the nearest whole number.
Atomic Mass

18. How to find number of protons6 C
CARBON
Atomic Number/ number of Protons
The number of Protons in atom is also the Atomic number, so therefore the Atomic number also represents the amount of Protons in the nucleus of that Atom.

19. How to Find the Amount of Neutrons in an Atom
To find the amount of neutrons in an atom you have to subtract the atomic mass from the atomic number . 16 S
sulfur
32.064 2 8 6
Atomic Mass
Number of protons 32
Atomic Number 16 16

20. To determine amount of electrons
To find the number of electrons in an atom, look at the numbers in the right side. To determine the number of energy levels count the number of side numbers and there you go!!! 6 C
CARBON 2 4

21. How to tell what period the element is listed33 AS
ARSENIC 2 8 18 5
APPEARS IN THE 4TH PERIOD
4 ENERGY LEVELS

22. What's the BIG difference
The big difference between an element, compound, and a molecule is……
Element: a substance made up of only 1 kind of atom
Compound: a substance made up of 2 or more DIFFERENT elements
Molecule: a grouping of 2 or more atoms joined together

23. For instance . . .
This is an atom of an element. As you can see, it is made up of only one kind of atom
. . In this case Hydrogen H

24. Now, with a compound O H O
When two or more atoms are put together it makes a compound.

25. How elements are formed
Elements are formed with a nucleus, and inside the nucleus is protons and neutrons. Around the nucleus are energy fields, and inside the energy fields are are electrons.
Sulfur

26. Vocabulary Electron Electron fields Neutron Proton Mass Nucleus
Compound
Atom
Isotope
element
Electron fields
Mass
Atomic structure
Periodic table
Chemical symbol

27. Suggested Vocabulary Element name chemist properties matter
electron cloud
synthetic
metal
metalloid
Solid
liquid
gas
noble gasses
subatomic
Nonmetals
particles

28. Check out some of these helpful websites to do some research of your own . . .
A periodic table of Elements
Periodic Table Adventure
Science Education at Jefferson Lab

29. Contributor's Jessica Osorio Rebekah Flores Morgan Chacon Karly Perez
Julian Rojas Nick Waldovogel
Tony Rinaldi
Lennis Montoya
Josh Quezada
Josh Olea
Jackie Cakmak