1. Atomic Structure
notes page 111

2. Average mass of atoms of element
# of protons in nucleus and the
# of electrons in a neutral atom
Average mass of atoms of element

3. Charge/Masses of Atomic Parts:
Protons Neutrons Electrons
positive charge (+)
mass of 1 amu
represented by atomic number
no/neutral charge (o)
negative charge (-)
mass is negligible (too small too care)
Represented by atomic number IF the atom is neutral (no charge)

5. To find the # of neutrons in an atom, subtract the atomic number from the atomic mass. (you can round!)
= 20

8. So why does the atomic mass have a decimal?

9. Isotope Variation of an element due to change in the # of neutrons
all atoms of a particular element with have the same # of protons, but the # of neutrons can vary.
ex.) Carbon-12, Carbon-13, and Carbon-14 are all isotopes of the element Carbon… each has only 6 protons, but 6, 7, and 8 neutrons, respectively.

11. Electrons
usually equal to # of protons, so charges cancel and the atom is neutral.
sort themselves into energy levels- only a certain number of electrons can fit on each energy level.

12. Energy Level # of Electrons Held (max.) 1st 2 2nd 8 3rd 18
*Each lower energy level must be filled before a new one can be created.

13. Energy Levels and Electron Configuration
Lower energy levels must be filled before a new level is created.
electrons in outermost energy level are called “Valence Electrons”

14. What makes noble gases so “noble?”

15. Practice electron configurations of elements