1. Atomic Theory
-a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms.

2. Democritus
-influential pre-Socratic philosopher -formulated an atomic theory -400 B.C.

3. John Dalton
1803
Solid Ball +

4. JJ Thomson Plum pudding 1897 Discovered Electrons Plum Pudding Model
Aka
Muffin Model
Arroz con Leche Model
Discovered Electrons

5. Neils Bohr
Electron
1913
Proton
Neutron
Nucleus

6. Ernest Rutherford
1909
Planetary Model
Discovered Protons

7. Louis de Broglie & Erwin Schrodinger
Electron Cloud Model
1926

8. 1927 Solvay Conference

9. Atomic Structure Notes

10. Element -substances that are the building blocks of all matter
-made up of one kind of atom
-Ex. Carbon, Hydrogen, Oxygen

11. Atom
-smallest particle of an element that maintains the properties of that element
-Consists of
Nucleus- center of the atom and makes up the mass of the atom
Electron Cloud -the negatively charged space that surrounds the atomic nucleus
Subatomic Particles
are found here

12. Subatomic Particles -a particle smaller than an atom
3 main Subatomic Particles
Protons
Neutrons
3. Electrons

13. Protons (+) particles found in the NUCLEUS of an atom.
have a POSITIVE charge

14. Neutrons Particles found in the NUCLEUS of an atom.
Have a NEUTRAL charge (no charge)

15. Electrons (e-)
Particles found in the ELECTRON CLOUD (orbiting the nucleus)
Have a NEGATIVE charge

16. Atomic Mass
average mass of one atom of an element (mostly from PARTICLES IN THE NUCLEUS)
Measured in AMU’s –Atomic Mass Unit
Protons plus neutrons in nucleus
Calculate number of neutrons by subtracting the atomic number from the atomic mass
AM-P=N

17. Sizes of Subatomic Particles
Protons
Neutrons
Electrons
.0005 AMU
So small some scientists also consider the mass 0 (Zero)
1 AMU
1 AMU

18. parts of an atom. Electron Cloud Nucleus Nucleus makes up 99.99%
of atomic mass

19. Atomic Number
-reflects the # of protons in the nucleus and electrons in the electron cloud of a balanced atom of that element.
ATOMIC NUMBER = # OF PROTONS & ELECTRONS

20. Atomic Number

21. Atomic Mass
-the sum of the protons and the average number of neutrons

22. Atomic Mass

23. # of Neutrons
Atomic Mass (rounded to nearest whole number) minus # of protons - AM p+ = N

24. AM-P=N Example
Using the formula above, solve for the correct number of neutrons for the following Elements and show your work (Use periodic tables in your agenda):
Al (Aluminum)
Sulfur (S)
Titanium (Ti)
Thalium (Tl)
Hydrogen (H)

25. Atomic Symbol

26. Putting it all together
Atomic Number
Element Symbol
Atomic Mass

27. Electron Orbitals aka Electron Shells aka Energy Levels
-the location and the path around the nucleus where an electron can be found -the amount of energy carried by an electron in an atom

28. Energy Level Maximum # of Electron’s each level can hold
Nucleus
2 e-

29. Nucleus

30. Valence Shell -the outermost shell of an atom in its uncombined state
-all atoms want their valence shells filled.

31. Valence Electron electrons located in the valence shell
# of valence e- will determine the reactivity of the atom.
The more Valence e’s the more stable and HAPPY (Noble Gases)
The less valence e’s the more reactive and EXPLOSIVE or UNHAPPY (Alkali Earth Metals)