1. Presentation Properties of Atoms
By : Vaibhav Sharma

2. Atoms Smallest particle that still retains properties
All matter is made up of atoms
Comes from Greek word atomos – meaning indivisible

3. Dalton’s Atomic Theory
Matter is composed of atoms
Atoms are indivisible
Atoms of a given element are identical in size, mass, chemical properties
Atoms of a specific element are different than those of another element

4. Components of the Atom Nucleus – consists of protons and neutrons
Protons – positively charged
Neutrons – neutral
Mass of protons and neutrons are similar
Electrons – orbit around the nucleus
Negatively charged
1/2000 mass of a proton

5. Electron Orbits Electrons “orbit” around the nucleus, called “shells”
Similar to planets orbiting around the sun
Called the “Bohr Model”
2, 8, 8, ….

6. Bohr Models
Carbon Bohr Model
Calcium Bohr Model
Argon Bohr Model

7. Valence Electrons Electrons in outermost shell
Important for chemical reactions

8. Atomic Number & Mass Number
Measures # of protons in the nucleus
Also measures # of electrons in a neutral atom
Mass Number
Measures mass of the nucleus: # protons + # neutrons

9. Isotopes
Different atoms may have different # neutrons – called isotopes
Ex: Carbon-12 has 6 protons 6 neutrons, Carbon-14 has 6 protons 8 neutrons
Different isotopes have different mass number.

10. Atomic Mass Weighted average of all isotopes – usually a decimal
Based on abundance in nature
Example: Chlorine-35, Chlorine-37: 35* * = 35.45

11. Elements
Pure substance that cannot be separated by physical or chemical means
Made of only 1 type of atom
Has unique properties

12. Periodic Table

13. Groups and Periods Groups are the columns on a periodic table
1,2,transition,3,4,5,6,7,8
Similar chemical properties in each column
Periods are rows on the periodic table
Goes from 1 to 7