The Periodic Table Atomic Structure and

History of the Periodic Table Mendeleev (1860’s) – Developed the first periodic table – It was arranged by atomic mass – He was able to predict properties of elements Moseley - developed the modern periodic table, arranged by atomic number (number of protons) Memory Trick: M & M created the periodic table…

Left of zig zag On the zig zag Right of zig zag METALS METALLOIDS NONMETALS II. Organization (your Roadmap) A. Metals- Nonmetals- Metalloids-

Characteristics of Metals Hard Shiny Conduct heat and electricity well Includes the transition and inner-transition metals – Inner transition metals include the lanthanoids and actinoids Characteristics of Nonmetals Are gases or brittle solids at room temp. Surfaces are dull Insulators Characteristics of Metalloids Have properties of both metals and nonmetals

Period vs. Group Period – All elements in a horizontal row – 7 periods on the periodic table

Group – All elements in a vertical column – Sometimes called “families” because they share similar properties

The Periodic Table -Elements are arranged according to increasing atomic number -rows are called periods -columns are called groups **The group number of an element will tell you the number of valence electrons for groups 1-2 and in groups the number of valence electrons is 10 fewer than the group number (except for helium which only has 2 valence electrons) For groups 3-12, other methods are used to determine their valence electrons.

Examples: -Hydrogen is in Group 1 so only has 1 valence electron -Oxygen is in Group 16 (16-10) so only has 6 valence electrons -Iodine is in Group 17 (17-10) so has 7 valence electrons

Group 1 (IA) – Alkali Metals-most reactive of all elements- only has 1 valence electron in outer shell

Group 2 (IIA) – Alkaline Earth Metals- very reactive- only has 2 valence electrons

Group 17 (VIIA) – Halogens- very reactive, never found uncombined in nature, tends to bond with metals to form salts

Group 18 (VIIIA) – Noble Gases- unreactive since stable. Outer shells are filled by valence electrons. Colorless, odorless gases

TRANSITION “Group B” INNER TRANSITION Group A & B REPRESENTATIVE “Group A” Group A- Representative Group B - Transition