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.

2.1 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

All elements are represented by symbols.

Here are just a few element symbol examples:

See page 44

Common ElementsHydrogen (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 CO2, the only by-product is H20 ! Yay water!!

See page 45

See page 45Oxygen (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!!!

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

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

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

Other Common Elements1) 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

Homework

Worksheet 2.1

(c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007