1. Daily Review Which scientist discovered the electron?
Which scientist discovered the nucleus?
Which scientist had the plum pudding model of the atom?
Which scientist used the gold foil experiment?
Which scientist described electrons as having set paths?
Which scientist believed that atoms were indivisible?

2. Atomic Structure
Chapter 4

3. Objectives
Identify the subatomic particles and understand placement and charge for each particle.
Understand the concept of an isotope and what makes one element different from another
Calculate the number of neutrons in an atom
Calculate the Average atomic mass of a isotope

4. The Atom
Matter is anything that takes up space and has mass. All matter is made of atoms.
Atoms are the basic building blocks of matter. They make up everything around us; Your desk, the board, your body, everything is made of atoms!
Atoms are too small to see without powerful microscopes.

5. The Atom There are two basic components in every atom: Electron Cloud
Nucleus

6. Subatomic Particles
There are 3 subatomic particles (well really, there are some smaller than these~)
Proton: Positively Charged, mass = 1.67 x , found in nucleus
Electron: Negatively Charged, mass = 9.11 x , found around the nucleus
Neutron: no charge, mass = 1.67 x , found in the nucleus

7. Atomic Number and Mass Number
Atomic Number (Z): number of protons in the nucleus of an atom
Identifies the element
Ex: an element with 1 proton is always hydrogen.
Mass Number (A): number of protons + neutrons in the nucleus of the atom

8. Finding p+ n0 and e- Number of Protons (Atomic number) = 22
Mass number
Number of Protons (Atomic number) = 22
Number of Electron (Same as protons in a neutral atom) = 22
Number of Neutrons (mass number – atomic number) = 26
Atomic Number

9. Finding p+ n0 and e- Mass number Atomic Number Protons Neutrons
Electrons 23 11 27 13
128 53
108 47

10. Isotopes and Atomic Mass
Isotope: Atom of the same element that differs in the number of neutrons. (this means mass will differ)
Example: Lithium-7 and Lithium -6
There are 2 isotopes
The first has 4 neutrons
The second has 3 neutrons

11. Average Atomic Mass
Average Atomic Mass: The weighted average mass of the atoms in a naturally occurring sample of an element.
Formula:
(Mass of isotope 1 x % abundance) + Mass of isotope 2 x % abundance) = average atomic mass

12. Example Problem

13. Practice, Practice, Practice!
Find the average atomic mass of carbon if carbon—12 has a % abundance of and carbon—13 has a percent abundance of 1.11.
Find the average atomic mass of element X if isotope 1 has a mass of amu (% abundance 19.91) and isotope 2 has a mass of amu (% abundance 80.09)

14. Closing: K-L-W On an index card list your KLW for the lesson
Know (previous knowledge)
Want to know (clarification)
Learned