1. Section 2.1 Introduction to elements Why are elements studied in chemistry? 1)Chemistry is the study of matter and its properties. 2)An element is a pure substance that cannot be broken down or separated into simpler substances. Each element is one kind of atom. 3)By studying elements, we can learn more about the structure of matter.

2. 2.1 Elements Element names and symbols 1)Because elements have different names in different languages, chemists use international symbols for them 2)Chemical symbols consist of one or two letters. 3)Ancient names are used as the source of many of the symbols. Example: Hydrogen (H) Hydros genes = water forming

3. All elements are represented by symbols. Here are just a few element symbol examples: See page 44

4. Common Elements Hydrogen (H) 1)Colorless, odorless, tasteless, and highly flammable gas. 2)Makes up over 90% of the atoms in the universe 3)Used in producing fertilizers 4)Lighter than air 5)Automobiles made to be run on hydrogen rather than gasoline. Why? No pollution like producing CO 2, the only by-product is H 2 0 ! Yay water!! See page 45

5. Oxygen (O) - gaseous element we breathe 21 % of the atmosphere Reacts with most other elements Major component of water which covers ¾ of our planet Our cells use oxygen to convert sugar into energy we can use Plants produce Oxygen as a by-product of photosynthesis. For your info, about 65% of your body’s mass is made of Oxygen!!!

6. Iron (Fe) -mixed with carbon to make steel -very strong metal - good structural material, but can rust when mixed with water and oxygen See page 45 Iron in a river turns water and rocks red

7. Sodium (Na) 1)Very soft metal that can even be cut with a knife !!! 2)It also reacts so fast and so violently with water 3)Cannot be used to even hold water-  would react and could cause an explosion (c) McGraw Hill Ryerson 2007

8. 1)Chlorine (Cl) - yellow-green gas that is highly toxic 2)Safe enough in pools (used to kill bacteria) but in high concentrations it can be deadly 3)It combines with sodium to form table salt ! Cl Chlorine Cl

9. Other Common Elements 1)Mercury (Hg) - liquid at room temperature metal. 2)Silver (Ag) - precious metal mined in British Columbia 3)Silicon (Si) - brittle, grey, semiconductor that is second most common element in Earth’s crust. See pages 46 - 47 Hg Ag Si

10. Homework Worksheet 2.1 (c) McGraw Hill Ryerson 2007