Groups of the Table and A Brief History The Periodic Table Groups of the Table and A Brief History

The Father of the Periodic Table—Dmitri Mendeleev Mendeleev (1834-1907) was the first scientist to notice a relationship between the elements Around 1865 he arranged his periodic table by atomic mass Said properties of unknown elements could be predicted by the properties of elements around the missing element

Dmitri Mendeleev

The Periodic Table Henry Moseley (1887-1915) later discovered that the periodic nature of the elements was associated with atomic number, not atomic mass.

The Periodic Table Column = Group or Family 18 columns on the Periodic Table Row = Period 7 rows on the Periodic Table

What does the information in the box tell me? 1 H 1.008 Atomic Number = # of protons and # of electrons Elemental Symbol Atomic Mass = # of protons plus neutrons

Metals, Nonmetals, and Metalloids Hydrogen (H) the only nonmetal on the metal side Nonmetals are on the right of the stair-step Metals are to the left of the stair- step Semi-metals, “metalloids,” touch the stair-step

VALANCE ELECTRONS The electrons that are in the outermost energy level of any atom. Examples: Hydrogen has 1 valance electron Boron has 3 valance electrons Oxygen has 6 valance electrons Argon has 8 valance electrons

8 VALANCE ELECTRONS In order to feel and be stable, all atoms would like to have 8 valance electrons. If they don’t already have 8 they will react very well and bond with others that can add up to 8. Example: Oxygen has 6 valance electrons and reacts very easily with 2 Hydrogen atoms to form H2O, water.

The Groups of the Periodic Table Group 1 or 1a: The Alkali Metals Most reactive metals on the PT Rarely found free in nature Charge of +1, 1 valence electron

Group 2 or 2a: The Alkaline Earth Metals Still quite reactive Charge of +2, 2 valence electrons

T he Groups of the Periodic Table Groups 3-12 or 3-12b: Transition Metals Found freely and in compounds in nature Charge is usually +2 but can vary—usually 2 valence electrons

Group 13 or 3a: Boron Family Charge is +3, 3 valence electrons

The Groups of the Periodic Table Group 14 or 4a: The Carbon Family Contains elements that can form unusual bonds (carbon and silicon) Charge is +4 or -4, contains 4 valence electrons

Group 15 or 5a: The Nitrogen Family Charge is -3, contains 5 valence electrons

The Groups of the Periodic Table Group 16 or 6a: The Oxygen Family Also known as the chalcogens Charge is -2, 6 valence electrons

Group 17 or 7a: The Halogens Most reactive nonmetals charge is -1, 7 valence electrons

Group 18 or 8a: The Noble Gases (The Inert Gases) Inert means Nonreactive, don’t normally react with other elements Charge is 0, 2 or 8 valence electrons

Special Rows on the PT Lanthanides We call these rare earth metals because they are rarely found on earth. Actinides