Chapter 6: The Periodic Table - Weebly

Chapter 6:The Periodic TableChapter summary6:1 History od the Periodic table1) Mendeleev’s Periodic table2) Problems with early periodic tables6:2Modern Periodic table1) Key points: Periodic law, Periods and Groups, 3 broad classes of elements2) Properties of the 3 classes of elements (Metals, nonmetals and metalloids)3) Sorting elements based on general properties (3-types)4) Sorting elements based on electron configuration (4-types)5) Periodic trends:a) Atomic sizeb) Ionization energyc) Ionic sized) ElectronegativityChemistry NotesDr. Chirie Sumanasekera10 /30/ 2017

6.1: History of the periodic table1)2)Mendeleev’s Periodic tableProblems with early periodic tables

History: Mendeleev’s periodic table For thousands of years only a few elements wereknown - Gold, Silver and copper As chemists began using the scientific method,the rate of discovery of elements increased Chemists used the properties of elements tosort them into groups. In 1869 Dimitri Mendeleev organized the knownelements into groups based on repeatingproperties and increasing atomic mass Mendeleev left spaces for elements still notdiscovered (?) as he predicted their propertiesand discovery In the late 1800s Gallium & Germanium whichhas properties similar to Mendeleev’spredictions for elements between Zn and Aswere discovered. Then his periodic tablegained acceptance.Mendeleev’s published periodic table from 1869

History: Problems with early periodic tables When Mendeleev created his periodic table, scientists did not know abouta) the structure of the atom orb) that atoms of each element had a unique number of protons (atomicnumber) Number of protons is the same in all isotopes of an element. Proton numbers aredifferent only between different elements So arranging elements based on atomic mass- the sum of protons and neutronsis not a good way to arrange elements based on their properties as it ignores theelements with chemically similar isotopes A better way to groups elements is by Atomic number – which is unique to eachelement.

6.2: The Modern Periodic Table

Modern Periodic Table: Organization of ElementsGroup:1234567891011121314151617Period: 12MetalsMetalloidsNonmetals34567Figure 6.5 (p:158)18

1) Key Points on the arrangement of Elements:1) Arranged in order of increasing atomic number (protons)2) 7 periods and 18 groups /columns3) Each period represents a Principle Energy Level (n 1 to n 7)4) More elements in higher numbered periods because there are more orbitalsin those energy levels5) Elements within a group have similar properties6) Properties of elements in a period change as you go from left to right butthe properties within a period repeat as you move from one to another period7) Three broad classes of elements: majority of the elements are metals (leftside), some are nonmetals (upper right) and in between these are a fewmetalloids8) Across a period elements become less metallic Periodic law: When elements are arranged in order f increasing atomic numberthere is a periodic repetition of their physical and chemical properties

2) properties of the3 classes of Elements1. Metals2. Metalloids3. Non metalsPercent of elements80%6%14%Heat conductionExcellentpoorMostly very poorElectrical conductionExcellentPoor (silicon chips made ofmixtures of Si and Bconduct well)Mostly very poorAt room Temperature:All Solid (except Hg) All solidSome are solid, gas (H, He, N, O, F,Cl and all noble gases*) and Br isa brown liquid**Ductile and malleable yesnonoHigh luster/sheenYesnoNot reallyToughnessUsually hardsoftRange from hard to softIn general:All have similarpropertiesHas both metal and nonmetal propertiesHas the opposite properties ofMetals and this group has greatvariation in properties*Noble gases: He, Ne, Ar, Kr, Xe, Rn**Ductile make into wiresMalleable can be hammered into shape

The Periodic Table Chapter summary 6:1 History od the Periodic table 1) Mendeleev’s Periodic table 2) Problems with early periodic tables 6:2 Modern Periodic table 1) Key points: Periodic law, Periods and Groups, 3 broad classes of elements