1. Chemistry Review

2. Let’s review APE MAN Bohr Model Atomic number=Protons=Electrons
Mass number-Atomic number=Neutrons
Bohr Model
Developed by Niels Bohr in 1913
Shows behavior of subatomic particles

3. Subatomic Particles Protons, Neutrons, Electrons
Protons and neutrons have a mass of about 1 amu (atomic mass unit)
Electrons have a mass of about amu
Most of the mass of an atom is in the nucleus.

4. Bohr Model First energy level can hold up to 2 electrons.
Second energy level can hold up to 8 electrons.
Third energy level can hold up to 8 electrons.
Lower energy levels must be filled before going to the next energy level.

5. Quick Quiz
Draw the Bohr’s model for an atom of Sodium.

6. Periodic Table Atomic number identifies an element.
Periodic table is arranged by groups and periods. Elements in groups or families have similar properties.
The number of energy levels in an atom is the same as the row or period number.
You should be able to locate the following on the periodic table: Alkali metals, Alkaline earth metals, lanthanides, actinides, transition metals, metalloids, nonmetals, halogens, noble gases

8. Quick Quiz I am a noble gas in period 3. What am I?
I am a metalloid in Group 13/3A. What am I?
I am a halogen in Period 5. What am I?
I am an alkali metal with 19 electrons. What am I?

9. Valence Electrons
The electrons located in the outermost energy level of the atom are called valence electrons. Elements located in the same column on the Periodic Table have the same number of valence electrons. Columns on the Periodic Table are called groups, or families.
We will not identify valence electrons for the transition metals.

10. Quick Quiz How many energy levels do the following atoms have:
Calcium?
Oxygen?
Helium?
Francium?
Lead?

11. Quick Quiz How many valence electrons do the following atoms have?
Boron?
Fluorine?
Lithium?
Krypton?
Arsenic?

12. Reactivity
Reactivity is a chemical property of elements. It describes how a substance responds, or reacts, to another element or compound.
Elements in a group have similar reactivity.
Atoms tend to lose, gain, or share valence electrons with other atoms when the energy levels are not completely filled.
Elements with completely filled energy levels are extremely stable and do not react with other elements. (Noble gases)

13. Reactivity
Elements that have 1, 2, or 7 valence electrons are very reactive.
These elements easily combine with other elements to form stable compounds.

14. Quick Quiz Which atoms will be more reactive? Lithium or Gallium?
Sodium or Beryllium?
Carbon or Fluorine?
Helium or Potassium?
Nitrogen or Argon?