1. 2/23/12 - Bellringer
Explain and draw what you think a water molecule looks like.

2. Chapter 22 – Chemical Bonds
22.1 – Stability in bonding

3. Objectives
Describe how a compound differs from its component elements.
Explain what a chemical formula represents.
Discuss why chemical bonding occurs.

4. Compounds When elements chemically combine
Often have chemical and physical properties that aren’t anything like those of the individual elements

5. NaCl = Table Salt How different…
Na = shiny, soft metal that reacts violently with water
Cl = poisonous greenish yellow gas
How different…
Physically?
Chemically?

6. Chemical Formula
Tells what elements a compound contains and the exact number of the atoms of each element in a unit of that compound
H2O
2 Hydrogen atoms and 1 oxygen atom in every unit of water
Subscript = written below
Superscript = written above

7. Chemistry Jokes Two chemists went into a bar. Why?
Chemist 1 asked for some H2O
Chemist 2 asked for some H2O too… and died horribly.
Why?

9. Atomic Stability
Atoms form compounds because electric forces between electrons and protons attract and hold atoms and molecules together

10. Noble gases Unusually stable
8 outer electrons = full valence shell
Atoms are stable when they have a full valence shell
Elements get full shells by forming compounds
Gain, lose, or share electrons

11. Electrons and Energy Levels
Period tells you how many energy levels the element has

12. How do elements fill outer energy levels?
They do this by combining with other atoms that also have partially complete outer energy levels.
As a result, each achieves stability.
Group 1 and 17 (7A) atoms combine easily. Why?

13. This illustration shows electron dot diagrams for sodium and chlorine.
When they combine, sodium loses one electron and chlorine gains one electron.

14. Sodium had only one electron in its outer energy level, which is lost to combine with chlorine in sodium chloride.
It drops down to a new outer energy level, and it is stable with eight electrons.

15. When atoms gain, lose, or share electrons, an attraction forms between the atoms, pulling them together to form a compound.
This attraction is called a chemical bond. A chemical bond is the force that holds atoms together in a compound.

16. In-Class Assignment/Homework
22.1 WKT

17. Plan 22.1 notes Lewis Dot Diagrams notes 22.2 notes 22.3 notes 22.1 WS
Practice sheet (non-compound)
22.2 notes
Dating game
Lewis Dot compound practice sheet
22.3 notes
Bond with a classmate