Chapter 2.1 Part 2 Elements By Sherry Totten

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?

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

Examples of Elements: The Periodic Table

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.

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

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

o O2 o + = MOLECULE OF OXYGEN

MOLECULE OF CARBON DIOXIDE CO2 + + = MOLECULE OF CARBON DIOXIDE CO2

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

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

Carbon Monoxide 1:1 Ratio

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

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

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.

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

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.