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

A. Mendeleev zDmitri Mendeleev (1869, Russian) yOrganized elements by increasing atomic mass yElements with similar properties were grouped together yThere were some discrepancies

A. Mendeleev yDeduced elements existed, but were undiscovered elements, their properties could be predicted

B. Moseley zHenry Moseley (1913, British) yOrganized elements by increasing atomic number yResolved discrepancies in Mendeleev’s arrangement yThis is the way the periodic table is arranged today!

C. Modern Periodic Table zGroup (Family) zPeriod

1. Groups/Families zVertical columns of periodic table zEach group contains elements with similar chemical & physical properties (same amount of valence electrons in each column) z2 numbering systems exist: yGroups # I through VIII with ea. # followed by A or B A groups are Main Group Elements (s&p electrons) B groups are Transition Elements (d electrons) yNumbered 1 to 18 from left to right

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

zMain Group Elements zTransition Metals zInner Transition Metals 3. Blocks

Lanthanides - part of period 6 Actinides - part of period 7 Overall Configuration

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

A. Metallic Character zMetals zNonmetals zMetalloids

1. Metals zGood conductors of heat and electricity zFound in Groups 1 & 2, middle of table in 3-12 and some on right side of table zHave luster, are ductile and malleable zMetallic properties increase as you go from left to right across a period

a. Alkali Metals zGroup 1(IA) z1 Valence electron zVery reactive, form metal oxides (ex: Li 2 O) zElectron configuration yns 1 zLowest melting points zForm 1+ ion: Cations yExamples: Li, Na, K

b. Alkaline Earth Metals zGroup 2 (IIA) z2 valence electrons zReactive (not as reactive as alkali metals) form metal oxides (ex: MgO) zElectron Configuration yns 2 zForm 2 + ions zCations yExamples: Be, Mg, Ca, etc

c. Transition Metals zGroups 3 – 12 (IB – VIIIB) zReactive (not as reactive as Groups 1 or 2), can be free elements zHighest melting points zElectron Configuration yns 2 (n-1)d x where x is column in d-block zForm variable valence state ions zAlways form Cations yExamples: Co, Fe, Pt, etc

3. Metalloids zSometimes called semiconductors zForm the “stairstep” between metals and nonmetals zHave properties of both metals and nonmetals zExamples: B, Si, Sb, Te, As, Ge, Po, At

2. Nonmetals zNot good conductors zUsually brittle solids or gases (1 liquid Br) zFound on right side of periodic table – AND hydrogen zHydrogen is it’s own group, reacts rapidly with oxygen & other elements (has 1 valence electron)

Nonmetal Groups/Families zBoron Group: IIIA typically 3 valence electrons, also mix of metalloids and metals zCarbon Group: IVA typically 4 valence electrons, also has metal and metalloids zNitrogen Group: VA typically 5 valence electrons, also has metals & metalloids zOxygen Group: VIA typically 6 valence electrons, also contains metalloids

a. Halogens zGroup 17 (VIIA) zVery reactive zElectron configuration yns 2 np 5 zForm 1 - ions – 1 electron short of noble gas configuration zTypically form salts (NaCl) zAnions yExamples: F, Cl, Br, etc

b. Noble Gases zGroup 18 (VIIIA) zUnreactive, inert, “noble”, stable zElectron configuration yns 2 np 6 full energy level yHave an octet or 8 valence e- zHave a 0 charge, no ions zHelium is stable with 1s 2, a duet zExamples: He, Ne, Ar, Kr, etc

B. Chemical Reactivity zMetals zPeriod - reactivity decreases as you go from left to right across a period. Group - reactivity increases as you go down a group zNon-metals zPeriod - reactivity increases as you go from the left to the right across a period. Group - reactivity decreases as you go down the group.

C. Valence Electrons zValence Electrons ye - in the outermost s & p energy levels yStable octet: filled s & p orbitals (8e-) in one energy level 1A 2A 3A 4A 5A 6A 7A 8A

C. Valence Electrons zYou can use the Periodic Table to determine the number of valence electrons zEach group has the same number of valence electrons zGroup #A = # of valence e - (except He) 1A 2A 3A 4A 5A 6A 7A 8A

D. Lewis Diagrams zAlso called electron dot diagrams zDots represent the valence e - zEx: Sodium zEx: Chlorine Lewis Diagram for Oxygen