1. REPRESENTATIVE GROUPS (5.3)

2. Valence Electrons
The “A” groups in the periodic table have numbers that match the number of valence electrons in an electron configuration for an element in that group
Valence Electron - an electron that is in the highest occupied energy level of an atom

3. Valence Electrons
These electrons play a key role in chemical reactions
Elements in a group have similar properties because they have the same number of valence electrons
Properties vary across a period (row) because the number of valence electrons increases from left to right

4. Alkali Metals (1A) Have a single valence electron Extremely reactive
Found in nature only as compounds
The reactivity increases from the top of group to the bottom

5. Alkali Metals Table salt is a compound of sodium and chlorine
Sodium is a soft metal that can be cut with a knife
It melts at about 980 C and has a lower density than water
It reacts violently with water like other elements in this group
Sodium and potassium are stored under oil to keep them from reacting with the oxygen and water vapor in air

6. Alkaline Earth Metals (2A)
Have 2 valence electrons
Harder than metals in 1A
Differences in reactivity among the alkaline earth metals are shown by the ways they react with water

7. Magnesium Helps plants produce sugar
A mixture of magnesium and other metals can be as strong as steel but much lighter
Frames of bicycles and backpacks often contain magnesium

8. Calcium Helps keep your bones and teeth strong
Calcium carbonate (compound of calcium, carbon, and oxygen) is the main ingredient in chalk, limestone, coral and pearl

9. The Boron Family (3A) 3 valence electrons
Boron, Aluminum, Gallium, Indium, and Thallium
Aluminum is the most abundant metal in Earth’s Crust and is often found combined with oxygen in a mineral called bauxite
Aluminum is strong, lightweight, malleable, and a good conductor of electric current

10. The Carbon Family (4A)
Contains Carbon (non-metal), silicon and germanium (metalloids), and tin and lead (metals)
4 valence electrons
More metallic as you go down the group
Life on earth would not exist without carbon
Except for water, most of the compounds in your body contain carbon

11. The Nitrogen Family (5A)
5 valence electrons
Nitrogen and Phosphorus (nonmetals), Arsenic and Antimony (metalloids), Bismuth (metal)
Nitrogen and Phosphorus are often found in fertilizers and your body uses compounds containing nitrogen and phosphorus to control reactions and release energy from food

12. The Oxygen Family (6A)
Oxygen, Sulfur, and Selenium (nonmetals) Tellurium and Polonium (metalloids)
6 valence electrons
Oxygen is the most abundant element in Earth’s crust
Complex forms of life need oxygen to stay alive because oxygen is used to release the energy stored in food

13. The Halogens (7A) 7 valence electrons
Flourine and Chlorine (gases), Bromine (liquid), Iodine (solid), Astatine (very rare)
Despite their physical differences, the halogens have similar chemical properties
They are highly reactive nonmetals and flourine is the most reactive

14. The Noble Gases (8A)
Helium only has two valence electrons but the rest have 8
Are colorless, odorless and extremely unreactive
Hard to discover these elements because they were colorless and odorless
Does not react easily with other elements and can be used to prevent reactions with highly reactive elements like oxygen