2.  Scientist used to believe that matter was made up of four elements (air, earth, fire and water).  We now know that all matter in the universe is made of slightly more than 100 different substances called elements.

3. Iron Copper Gold  Element - a pure substance that cannot be broken down into any other substances by chemical or physical means.  Elements are the simplest substances.

4.  The elements do not only exist alone … they combine with other elements to make all the matter in the world.  All living things, including humans, are made mostly of just six elements  The six elements found in the amount in living things are:  N itrogen  Carbon  Hydrogen  Oxygen  Phosphorous  Sulfur  The way to remember it this is N’CHOPS. Pork Chops, N’CHOPS

5.  Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on their mass  He lived from 1834- 1907

7.  Atomic number is on top  The symbol is in the middle.  Can be one capital letter like “O” for oxygen  Can be one capital letter and one lowercase like “Au” for gold when there are two letter abbreviations.  Element name MAY OR MAY NOT BE LISTED WITH THE SYMBOL!  The atomic mass is below the symbol.

8.  The periodic table was originally organized by increasing mass (Mendeleev).  The modern periodic table is organized by increasing atomic number.  The number starts at 1 with Hydrogen, increases going to the right with Helium, 2.  It then jumps down a row and starts to the far left with Lithium, 3 and continues with this pattern until you get to the sixth row and we will discuss.

10.  Period – the name for each row of elements (left to right)  Family – the name for each column of element ( up and down)

11. THE PERIODIC TABLE PICTURES

12.  What is the smallest possible piece of matter?  All matter is made up of atoms.  Atom - is the basic particle from which all elements are made.

13.  All atoms are made of the same 3 subatomic (smaller than an atom) particles. Protons Electrons Neutrons

14.  Different elements have different properties because their atoms are different.  The hydrogen atom has 1 proton and 1 electron  The helium atom has 2 protons, 2 neutrons, and 2 electrons.

15. Atoms are made of protons (+), neutrons (no charge- neutral), and electrons (-). The number of protons determines which elements can be formed from the atoms Remember, the atomic number of an element tells you the number of protons in that element

16.  Atoms of most elements have the ability to combine with other atoms.  When atoms combine, they form a chemical bond,  Chemical Bond - a force of attraction between two atoms.

17.  In many cases, atoms combine to form larger particles called molecules.  Molecules – when two or more atoms join together by chemical bonds.  For Example: A molecule of water is made of a 2 different elements and three atoms total, H 2 O.  H – 2 atoms of Hydrogen as shown by the subscript 2  O – 1 atom of Oxygen (anytime there is not a subscript after an element, it is assumed to be a 1) (we will discuss this again)

19.  Two atoms of the same element can also combine to form a molecule.  Oxygen molecules consist of two oxygen atoms.  There are 7 elements that combine to form DIATOMIC molecules in nature – Hydrogen (H 2 ), Nitrogen (N 2 ), Oxygen (O 2 ), Fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ), and Iodine (I 2 )

20.  Compound - a molecule that contains at least two different elements  All compounds are molecules BUT not all molecules are compounds.  Remember…..A molecule is formed when two or more atoms join together chemically.  Diatomic hydrogen (H 2 ), diatomic oxygen(O 2 ) and diatomic nitrogen (N 2 ) are not compounds because each is composed of a SINGLE element.  Water (H 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ) are compounds because each is made from more than one element.  The smallest bit of each of these substances (COMPOUNDS) would be referred to as a molecule.  For example, a single molecule of diatomic hydrogen is made from two atoms of hydrogen while a single molecule of water is made from two atoms of hydrogen and one atom of oxygen.

21.  CO 2  The number 2 below the symbol for oxygen tells you that the ratio of carbon to oxygen is 1 to 2.  There is 1 Carbon atom for every 2 Oxygen atoms. (Anytime there is not a subscript after an element, it is assumed to be a 1)

22.  If a different ratio of carbon atoms to oxygen atoms are seen in a formula, you have a different compound.  CO  Carbon to oxygen ratio is 1 to 1.  There is 1 Carbon atom for every 1 Oxygen atom.  For example, Carbon Monoxide – a gas produced in car engines – has the formula CO.  Carbon Dioxide – a gas we exhale – has the formula CO 2

23.  When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements.

24. SULFUR AND SILVER - UNCOMBINED SULFUR AND SILVER – BONDED IN A COMPOUND  For example, the element sulfur is a yellow solid and the element silver is a shiny metal.  When silver and sulfur combine, they form a compound called silver sulfide, Ag 2 S. You would call this black compound tarnish.