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THE PERIODIC TABLE and PERIODIC LAW Essential Questions * How can we organize all the different elements? * How can the periodic table help us organize our chemistry knowledge? * What can we predict about elements based on their classification &location on the periodic table? II. WHY IS THE PERIODIC TABLE IMPORTANT? III. WHAT DOES THE WORD “PERIODIC” MEAN? A. DEFINITION-Happening or repeating at regular intervals Cyclic - happening in a cycle B. EXAMPLES OF OTHER EVENTS THAT ARE PERIODIC- Phases of moon Tides Seasons IV. HISTORICAL DEVELOPMENT OF THE PERIODIC TABLE A. How was the Periodic Table developed? • Done by many scientists • Tried to arrange elements in groups of three • Based on Dalton's atomic theory • Not very successful • Found that when arranged by mass, the eighth element was similar in physical and chemical properties • Related it to a musical scale • Called Newland's octaves DMITRI MENDELEEV Why is he considered the “Father of the Periodic Table”? LOTHAR MEYER Worked at the same time as Mendeleev. Both men demonstrated a connection between atomic mass and properties of elements. However, Mendeleev given more credit. WHY??? He Published First! Why the blanks? Giant Wall Periodic Table erected in St. Petersburg, Russia in 1934 2. ORGANIZATION OF MENDELEEV’S TABLE 3. LEFT BLANKS Mendeleev left spaces on the table where he thought undiscovered elements should go. 4. ORIGINAL PERIODIC LAW-The physical and chemical properties of elements are periodic functions of their atomic mass. 5. MODIFICATION OF PERIODIC LAW Locate several elements on the current table that are not arranged according to increasing atomic mass. Examples: Co 58.93 & Ni 58.69 Te 127.60 & I 126.90 Th 232.04 & Pa 231.04 U 238.03 & Np 237.05 Mendeleev’s table not completely correct. C. HENRY MOSELEY 1887-1915 1. In 1913, Henry Mosely discovered that atoms of each element had a unique atomic number. 2. Arranged elements by atomic number, not atomic mass. 3. Eliminated problems from Mendeleev's table D. MODERN PERIODIC LAW-- STATES THAT WHEN THE ELEMENTS ARE ARRANGED BY INCREASING ATOMIC NUMBER, THERE IS A PERIODIC REPETITION OF THEIR CHEMICAL AND PHYSICAL PROPERTIES V. ELEMENTAL INFORMATION ON THE PERIODIC TABLE A. READING SQUARES OF THE PERIODIC TABLE mass 35.45 Cl chlorine Atomic # 17 Squares of the Periodic Table VI. ORGANIZATION OF THE PERIODIC TABLE A. PERIODS 1. Definition---a horizontal row of elements on the Periodic Table --also called a “Series” 2. Energy levels and periods---the number of the period is equal to the number of “rings” of electrons around the atom **How many energy levels are in each element in Period 5? B. GROUPS 1. Definition---a vertical column of elements on the Periodic Table --also called a “Family” 2. Valence electrons and group number---each element within a group has the same number of valence electrons --In general, the group number is equal to the number of valence electrons --For group numbers greater than 10, the number of valence electrons is the ones place B. GROUPS **How many valence electrons are in Group 2 elements? **How many valence electrons are in Group 16 elements? 3. CLASSIFYING THE ELEMENTS a. Alkali Metals-- Group 1 elements except Hydrogen. Most reactive metals on the Table. Have 1 valence electron. b. Alkaline Earth Metals- Group 2 elements. Very active metals. Have 2 valence electrons. c. Transition Metals- Groups 3-11 elements. Typically less reactive than Alkali and Alkaline Earth Metals. Produce colored solutions. d. Halogens- Group 17 elements. Most nonmetallic elements on the table. Have 7 valence electrons e. Noble Gases- Group 18 elements. Extremely unreactive. Often called “inert”. Have 8 valence electrons except He which has only 2. f. Two Rows at the Bottom-- Lanthanide Series-Elements 57 – 71. Actinide Series-Elements 89 - 103 VII. PERIOIDIC TRENDS •As we can see, elements are grouped on the Periodic Table according to their physical and chemical properties as well as their electron configurations. •This creates the periodic repetition on the table, and allows us to see certain trends in these properties. Trends on the Table • Atomic radius • Ionization energy • Electronegativity • Each of these show trends as you move across a period AND down a group Major Element Grouping • The combination of periodic characteristics creates three broad categories of elements on the table: • Metals • Nonmetals • Metalloids Major Element Grouping • Described in relationship to the staircase that runs on the right-hand side of the table • Elements to the RIGHT of the staircase = NONMETALS • Elements to the LEFT of the staircase = METALS • Elements touching staircase (except Al) = METALLOIDS F. Metallic and Nonmetallic Properties Can help us characterize an element simply by knowing its placement on the PT Metals • Lose electrons easily to get to "magic number" of 8 • "Metals are losers" • Losing electrons makes them form an ION = charged atom • Most metallic elements = lower left of table REVIEW: What is an Ion? An atom that has lost or gained electrons and thus has acquired a charge. Cation-A positively charged atom PLUSSY CATS!! Nonmetals • Gain electrons easily to get to "magic number" of 8 • Nonmetals are "gainers" • Most non-metallic elements - upper right side of table Anion-A negatively charged atom "Cat chaser"