1. The Periodic Classification of Elements

2. Dmitri Mendeleev (1834 – 1907) A High School Science Teacher! He saw a pattern in the way the known elements reacted. He organized the elements according to this pattern.

3. He predicted the existence of elements that had not yet been found. Scientist later discovered these elements!

4. How Mendeleev organized the table Each box represents a different element The box contains; - The name of the element (ex. calcium) - The symbol of the element (ex. Ca) - The atomic number (calcium = 20) This is the number of protons, which is equal to the number of electrons in the atom. - The atomic mass (calcium = 40.078) This is the combined number of protons plus neutron in the nucleus. (ex., calcium has 40 – 20 = 20 neutrons)

5. He put the metals on the left and the non-metals on the right, with ‘metalloids’ in the middle.

6. Metals Are found on the left of the ‘staircase’ of the periodic table. Metals are; – Conduct electricity & heat – Ductile & malleable Can be shaped in wire or into sheets – Shiny – Solid at room temperature Except mercury (liquid) – Many react with acid

7. Are found on the right of the ‘staircase’ (except hydrogen). Non-metals are; – Poor conductors of electricity & heat – Many are gases at room temperature – Reduce to powder Non-Metals

8. Consists of 7 elements Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium & Astatine Metalloids; – Have properties of both metals and nonmetals. – Sometimes are good conductors of electricity. – Can be used to make semiconductors Metalloids

9. He put elements with similar chemical behavior in the same column, These are called the Families of the periodic table. We will give closer attention to four of the families, shown here as the first, second, seventh and the eighth (0 here).

10. The Alkali Metals Are found in the first column (except for hydrogen) lithium, sodium, potassium, rubidium, cesium, francium (get more reactive toward the bottom) - Are highly reactive and must be stored in oil (they will react explosively with water) -Are not found in their elemental state in nature (are in compounds with other elements) - Are soft and malleable

11. The Alkaline Earth Metals Are found in the second column beryllium, magnesium, calcium, strontium, barium, radium – Are highly malleable – Somewhat reactive (a bit less than the alkali metals) – Burn easily in presence of heat – Not found in their elemental state in nature (are found as a compound)

12. The Halogens – Are found in the seventh column (column 7A, second from the right) fluorine, chlorine, bromium, iodine, astatine – Are non-metals – React easily to form compounds ex., table salt (NaCl) – Are powerful disinfectants Ex. Chlorine

13. The Noble Gases Are found in column 8A (right side of the table) helium, neon, argon, krypton, xenon, radon, ununoctium – Are very stable (they rarely react with other elements) – Are found in their elemental state in nature – Are colorless, odorless

14. These are called the transitional metals. They’re also called the ‘B’ group. They include many important metals but we don’t get into them closely. Column 3A is called the boron family (or group) Column 4A is the carbon family Column 5A is the nitrogen group Column 6A is the oxygen group The Other Parts of the Periodic Table

15. The Periods of the Periodic Table The Periods are the rows of the periodic table – The period number of an element is equal to the number of orbitals its atoms have (also called electron shell or energy level).

16. Periodicity of Properties Certain properties show patterns that repeat from one period to another. melting & boiling point, atomic radius, electronegativity, etc.