I. Development of the Modern Periodic Table (p. 174 - 181) Ch. 6 - The Periodic Table & Periodic Law I. Development of the Modern Periodic Table (p. 174 - 181)

A. Mendeleev Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass Elements with similar properties were grouped together There were some discrepancies

A. Mendeleev Dmitri Mendeleev (1869, Russian) Predicted properties of undiscovered elements

B. Moseley Henry Moseley (1913, British) Organized elements by increasing atomic number Resolved discrepancies in Mendeleev’s arrangement This is the way the periodic table is arranged today!

C. Modern Periodic Table Group (Family) Period

1. Groups/Families Vertical columns of periodic table Numbered 1 to 18 from left to right Each group contains elements with similar chemical properties

2. Periods Horizontal rows of periodic table Periods are numbered top to bottom from 1 to 7 Elements in same period have similarities in energy levels, but not properties

3. Blocks Main Group Elements Transition Metals Inner Transition Metals

3. Blocks Overall Configuration Lanthanides - part of period 6 Actinides - part of period 7

II. Classification of the Elements (pages 182-186) Ch. 6 - The Periodic Table II. Classification of the Elements (pages 182-186)

A. Metallic Character Metals Nonmetals Metalloids

1. Metals Good conductors of heat and electricity Found in Groups 1 & 2, middle of table in 3-12 and some on right side of table Have luster, are ductile and malleable

a. Alkali Metals Group 1 1 Valence electron Very reactive Electron configuration ns1 Form 1+ ions Cations Examples: Li, Na, K

b. Alkaline Earth Metals Group 2 Reactive (not as reactive as alkali metals) Electron Configuration ns2 Form 2+ ions Cations Examples: Be, Mg, Ca, etc

c. Transition Metals Groups 3 - 12 Reactive (not as reactive as Groups 1 or 2), can be free elements Electron Configuration ns2(n-1)dx where x is column in d-block Form variable valence state ions Cations Examples: Co, Fe, Pt, etc

2. Nonmetals Not good conductors Found on right side of periodic table – AND hydrogen Usually brittle solids or gases

a. Halogens Group 17 (7A) Very reactive Electron configuration ns2np5 Form 1- ions – 1 electron short of noble gas configuration Anions Examples: F, Cl, Br, etc

b. Noble Gases Group 18 Unreactive, inert, “noble”, stable Electron configuration ns2np6 full energy level Have a 0 charge, no ions Examples: He, Ne, Ar, Kr, etc

3. Metalloids Sometimes called semiconductors Form the “stairstep” between metals and nonmetals Have properties of both metals and nonmetals Examples: B, Si, Sb, Te, As, Ge, Po, At

B. Chemical Reactivity Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases

C. Valence Electrons Valence Electrons e- in the outermost energy level Group #A = # of valence e- (except He) 1A 2A 3A 4A 5A 6A 7A 8A

C. Valence Electrons Valence electrons = electrons in outermost energy level You can use the Periodic Table to determine the number of valence electrons Each group has the same number of valence electrons 1A 2A 3A 4A 5A 6A 7A 8A

D. Lewis Diagrams Ex: Chlorine Also called electron dot diagrams Dots represent the valence e- Ex: Sodium Ex: Chlorine Lewis Diagram for Oxygen