1. Chapter 2.1 Part 2 Elements By
Sherry Totten

2. An ELEMENT is a PURE SUBSTANCE that cannot be broken down into any other SUBSTANCE by PHYSICAL OR CHEMICAL means.
Oxygen
Hydrogen
Iron
What is an element?

3. Elements are the Simplest Substances
Each element can be defined by its PHYSICAL AND CHEMICAL properties.
Chemical Properties of Gold
Gold is not very chemically reactive.
It will react with Chlorine and Fluorine Gases. The amount to cause reaction would destroy your lungs!
Elements are the Simplest Substances

4. Examples of Elements: The Periodic Table

5. Elements are represented by one or two letter symbols.
H = Hydrogen
O = Oxygen
C = Carbon
Fe = Iron
Na = Sodium
Elements are represented by one or two letter symbols.

6. The ATOM is the smallest possible piece of matter.
The Atom is the basic PARTICLE that all of the elements are made up of.
We have different elements with different properties because each element is made up of DIFFERENT ATOMS!
Particles of Elements

7. Atoms of most elements have the ability to COMBINE with other atoms.
When atoms combine they form a CHEMICAL BOND.
When 2 or more atoms combine they form a MOLECULE. H H + + O =
When Atoms Combine

8. o O2 o + =
MOLECULE OF OXYGEN

9. MOLECULE OF CARBON DIOXIDE CO2+ + =
MOLECULE OF CARBON DIOXIDE CO2

10. COMPOUNDS (When Atoms Chemically bond with atoms they form molecules.)
When elements chemically combine with other elements they become a COMPOUND.
A COMPOUND is a pure substance made of two or more elements in a set ratio.
COMPOUNDS

11. A COMPOUND is represented in a CHEMICAL FORMULA that shows the ELEMENTS that exist in the compound
And the ratio of their ATOMS
CO2 = contains elements Carbon & Oxygen
The Ratio is 1:2 or
1 Carbon for every 2 Oxygen atoms.
CHEMICAL FORMULA

12. Carbon Monoxide 1:1 Ratio

13. Compounds are Pure Substances
This means that after the elements are chemically combined to form the compound, the compound has UNIQUE properties.
These properties are different than the ELEMENTS that formed the compound!
We have an entirely new substance!
Compounds are Pure Substances

14. Table Sugar is a Compound
The Chemical formula for table sugar is C12H22O11
This compound no longer has the properties of the gases from which it was made.
Table Sugar is a Compound

15. What is the difference between an molecule and a compound?
A molecule is formed when two or more atoms join together chemically.
A compound is a molecule that contains at least two different elements chemically combined.
All compounds are molecules but not all molecules are compounds.

16. Molecular Hydrogen (H2), molecular Oxygen (O2) and molecular Nitrogen (N2) are not compounds because each is composed of a single element.
Molecule = 2 atoms chemically combined
Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element.
Compound = 2 or more different elements
chemically combined

17. ATOMS are the smallest possible piece of matter.
Summary:
ATOMS are the smallest possible piece of matter.
ELEMENTS is the smallest pure substance that can not be broken down into other substances. Elements show the different TYPES OF ATOMS.
We have different elements because we have different kinds of atoms.
ATOMS COMBINE to form MOLECULES. Atoms can combine with other like atoms or with different atoms. They are all MOLECULES.
When ELEMENTS combine with 2 or more different ELEMENTS they form COMPOUNDS.
COMPOUNDS are represented by CHEMICAL FORMULAS to show both: the kinds of elements that make them up and the ratio of atoms for each of the elements
All Compound are also Molecules.
Only Molecules made of 2 or more different atoms are compounds.