1. Chemistry of Life
Chapter 2

2. Warm Up 8/22
Try to recall the following information without referencing your textbook or a friend
What is an atom?
What is an element?
What differentiates one element from another?
What are protons, neutrons and electrons?

3. Answers Atom: basic unit of matter Element: a specific kind of atom
Made up of 3 smaller particles
Neutrons- no charge “neutral.” Found in nucleus
Protons- positive charge. Found in nucleus
Electrons- negative charge. Tiny. Orbit nucleus in a 3D “electron cloud”
Element: a specific kind of atom
Determined by number of PROTONS
Examples?

5. In red you see the short cut that shows how many valence Electrons

6. Element name
Atomic Number
Element Symbol
Atomic Mass

7. Atomic Number and Atomic mass
Number of protons in that element (also equals the number of electrons)
Atomic mass
Mass of protons and neutrons
*find the number of neutrons by:
Atomic mass – atomic number

8. Bohr’s Atomic Model Nucleus in center (protons and neutrons)
Electrons are in energy levels/energy shells surrounding the nucleus
Energy level 1 holds up to 2 electrons
Energy level 2 holds up to 8 electrons
Energy level 3 holds up to 18 electrons
There are 91 elements on the periodic table. 25 exist in living things. We will not go beyond 3rd energy level. 4 holds 32, then 50, then 72

9. Stability and Octet Rule
An atom is stable if its outer shell is full OR has eight electrons (octet rule)
The outer shell is known as the VALENCE shell
The number of electrons in the valence shell determines the reactiveness of the the element
The closer to stable, the more reactive
If the shell is full, the atom is non-reactive
Noble gases

11. Let’s draw some atoms *list the number of valence electrons for each
Hydrogen
Helium
Oxygen
Neon
Magnesium

12. Unstable Atoms “like” to form bonds to become stable
Ionic bonds
Covalent bonds

13. Warm Up 8/21 Draw a fluorine atom
How many valence electrons does it have?
What does that say about its reactivity?
Draw a fluorine ion

14. Today 8/22 Review ions Atoms that have gained/lost electrons
Example: sodium ion
Learn about ionic bonding
Example: lithium chloride

15. Ionic Bonds
Attraction between oppositely charged ions

16. Covalent Bonds
Sharing of valence electrons
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