1. Introduction to Atoms
Exploring Inner Space

2. Atom The smallest particle of an element… makes up all matter.

3. Proton + +1 amu Neutron 0 (neutral) Electron - 0 amu
Particle
Charge
Mass
Proton +
+1 amu
Neutron
0 (neutral)
Electron -
0 amu
amu= atomic mass unit

4. The most stable form of an atom is electrically neutral… this means that the number of protons & electrons is equal.

5. Example=> Oxygen has 8 protons & 8 electrons

6. Nucleus: The center of the atom (contains protons & neutrons).

7. Electron cloud: electrons orbit the nucleus. (contains ONLY electrons).

8. The electrons fill energy levels within the electron cloud.

9. As a general rule, there are 2 electrons in the first energy level, up to 8 electrons in the second & 8 or more in each level after that.

10. Elements are atoms with the same number of protons that share the same physical & chemical properties… the # of protons determines the element.
For example, hydrogen has only 1 proton in its nucleus, Lithium has 3 protons, and Oxygen has 8.

11. Atomic number = the number of protons in an atom
How many protons does carbon have? 6

12. Almost all of the mass of an atom is in the nucleus.

13. Atomic mass =
# of protons +
# of neutrons

14. Carbon’s atomic mass is 12. Carbon has how many neutrons?6
(atomic mass - # of protons = # of neutrons)

15. Every element is represented by a symbol… if it has one letter, that letter is capitalized (C=carbon). If it has two letters, the first is capitalized & the second is lower case.
(Na = sodium)