1. Combinations of Atoms
Chapter 4.2
Page 87

2. Organization of the Periodic Table
Each Box gives information about one element
Name of element
Atomic number (number of protons)
Atomic Symbol
Atomic Mass

3. Position shows electron arrangement
Periods—horizontal rows
Give number of electron shells used

4. Groups Groups—vertical columns
Within a column elements have the same number of valence electrons

6. Atoms are the building blocks of molecules
water molecule

7. Molecules
The smallest unit of matter that can exist by itself and retain all of a substances chemical properties
In a molecule two or more atoms are bonded together

8. Diatomic molecules di--two
Some molecules are made of the same kind of atom O2

9. Ozone is O3

10. Chemical Formulas
A combination of letters and numbers that shows the number of atoms of each element that are required to make a molecule of the compound

11. Chemical Equations
Elements and compounds often combine through chemical reactions
The reaction can be described in a formula

12. Photosynthesis formula
6H2O + 6CO > C6H12O6+ 6O2
Reactants on left products on right
The arrow is read yields

13. Balanced equations
An equation is balanced when the number of atoms on the right equals the number of atoms of the same element on the left
To balance a formula you use coefficients

14. Photosynthesis formula
6H2O + 6CO > C6H12O6+ 6O2
What is the blue arrow pointing to?
What is the red arrow pointing to?

15. CO2
H2O

16. Book example
Magnesium, Mg, reacts with oxygen, O2, to form MgO, magnesium oxide
Write a balanced equation.
We have two oxygen on the right so we will need a number 2 on the left as a coefficient
2 Mg + O MgO

17. Chemical Bonds chemical bonds
The forces that hold together the atoms in molecules are called
chemical bonds
Bonds form because of attraction between opposite charges
Atoms can share or transfer valence electrons

18. Ions
When an electron is transferred from one atoms to another both atoms become charged
A charged particle like an atom or molecule is an ion

19. Cat lover or cat hater

20. A positively charged ion is a cation (+)

21. A negatively charged ion is called an anion (-)

22. Ionic Bonds
Attractive force between two oppositely charged ions that result from the transfer of electrons from one atom to another is called
An ionic bond

23. Na from the left wants to give away
Cl from the right wants to gain electrons
Ionic bonds form from atoms from opposite sides of the periodic table

24. Covalent Bonds
A bond between atoms that share electrons is called a covalent bond

25. Polar Covalent Bonds
Some atoms that are covalently bonded do not equally share elections
A covalent bond with unequal attraction is called a polar covalent bond
Water is one example

26. Metallic Bonds Electrons flow easily They are not tightly bound
This explains the properties of metals

27. Electron From Greek word for amber
Ben Franklin found electricity was a flow of electrons

28. Ben Franklin found electricity is the flow of electrons

29. Physical Change
A change of matter from one form to another without a change in chemical properties
Break
Crush
Melt
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30. Change of State is a physical change
An item can change from solid to liquid to gas and still have the same chemical formula
140

31. Dissolving is a physical change
Example: dissolve salt in water
You still have salt and water
You could evaporate the water and get the salt back
Something that dissolves is soluble
140

32. Chemical Changes
Form new substances with different physical properties
Can be detected
Fizz
Smell
Color
Produce heat
Produce a sound
Cannot be reversed by physical means
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33. Exothermic—produce heat
Endothermic—solution gets colder

34. Mixtures
A combination of two or more substances that are not chemically combined
Two types:
Heterogeneous--different
Homogenous--same

35. Heterogeneous mixtures
Two or more substances are not uniformly distributed
Example
Granite

36. Homogenous mixture
Having the same composition throughout

37. Solution
A homogenous mixture of two or more substances that are uniformly dispersed
When a substance dissolves it goes into solution
Example salt in water

38. Compounds can be broken down by physical means
Carbonic acid in pop gives it fizz
When the bottle is opened the acid breaks down into carbon dioxide and water
Carbon dioxide escapes as bubbles

39. Mixtures can be physically separatedBy
Density
Solubility
Magnetism
Lab Activity
Design an experiment to separate the mixture in your sample—list the steps you will take below
Be sure to clean up your area when you are through
141

40. Test for the presence of CO2 and H2
A flaming splint is used to detect the presence of carbon dioxide or hydrogen gas
CO2 extinguishes the flame
H2 Creates a hydrogen burp
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