1. Pretest This will not be graded!!!
Do the best you can to help me get an accurate idea of your knowledge.

2. Atoms Protons- positively charged Neutrons- neutrally charged
Electrons- negatively charged
Where does an atom’s mass come from?
Electrostatic force holds the protons and neutrons together in the nucleus
Electrons have 1/1840 the mass of a proton. But what is mass?
Atoms have the same number of protons and electrons- therefore the atom is neutral

3. Elements Element- substance that is made up of only one type of atom
Four most common elements in nature include oxygen, nitrogen, carbon, and hydrogen

4. Isotopes Atoms of an element may have different numbers of neutrons
Radioactive isotopes- decay over time at a certain rate
Total number of protons and neutrons in the nucleus of an atom is known as its mass number

5. Chemical Compounds
Substance formed by the chemical combination of two or more elements in definite proportions
Chemical formulas represent compounds H2O

6. Ionic Bond
Transfer of electrons between atoms

7. Covalent Bond
Sharing of electrons between atoms

8. Van der Waals Forces
Electrons move around a lot and cause temporary positive and negative areas.
This can cause a temporary attraction between molecules

9. Read pg. 39 Connection to Real World
What are some situations in which adhesive bandages don’t stay on very well?
Why don’t bandages stay on well in these situations?
What do doctors typically use to hold together tissues after surgery?
Why might bandages be a better alternative?