2. Development of Periodic Table Law of Triads Law of Octaves Elements could be classified into groups of three, or triads. Trends in physical properties such as density, melting point, and atomic mass were observed. Arranged the 62 known elements into groups of seven according to increasing atomic mass. He proposed that an eighth element would then repeat the properties of the first element in the previous group. Johann Döbereiner (1817) John Newlands (1863)

3. Dimitri Mendeleev was a Russian chemist in the mid-1800s. Mendeleev cataloged thousands of facts about the 63 elements known at the time. He became convinced that groups of elements had similar, "periodic" properties. Elements on Mendeleev's table were arranged according to their increasing atomic weight, leaving blank spaces where he was sure other, unknown elements would fit. Because of this, Mendeleev is considered to be the Father of the Periodic Table

5. Fifty years after Mendeleev, the British scientist Henry Moseley discovered that the number of protons in the nucleus of a particular type of atom was always the same. When atoms were arranged according to increasing atomic number, the few problems with Mendeleev's periodic table disappeared. Because of Moseley's work, the modern periodic table is based on the atomic numbers of the elements. Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers. 1954 Periodic Table

6. Modern Periodic Table Henry G.J. Moseley Determined the atomic numbers of elements from their X -ray spectra (1914) Arranged elements by increasing atomic number Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers. 1887 - 1915

7. Glenn Seaborg: Present day periodic table After discovering U, Th, Pa, Seaborg was advised to revise the periodic table. After examining the properties of the elements, Seaborg was convinced that the elements were part of the inner transition elements because they behaved similarly to these elements. Instead of creating a new system, he integrated the elements into a new section called the actinide series, which is part of the inner transition elements.

8. Glenn T. Seaborg He is the only person to have an element named after him while still alive. 1912 - 1999 "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."

9. P ZnAs Sb PtBi Midd. -1700 CrMn Li K NOF Na BBe H AlSiCl CaTiVCoNiSeBr SrYZrNbMoRhPdCdTeI BaTaWOsIr Mg CeTbEr ThU 1735-1843 Discovering the Periodic Table C S FeCu AgSn AuHgPb Ancient Times He ScGaGe RbRuIn CsTl PrNdSmGdDyHoTmYb La 1843-1886 Ne Ar Kr Xe PoRn Ra EuLu Pa Ac 1894-1918 Tc HfReAt Fr Pm NpPuAmCmBkCfEsFmMdNoLr 1923-1961 Rf Db SgBhHsMt 1965- Journal of Chemical Education, Sept. 1989

10. Introduction to the Periodic Table Elements are arranged in seven horizontal rows, in order of increasing atomic number from left to right and from top to bottom. Rows are called periods and are numbered from 1 to 7. Elements with similar chemical properties form vertical columns, called groups, which are numbered from 1 to 18. Groups 1, 2, and 13 through 18 are the main group elements. Groups 3 through 12 are in the middle of the periodic table and are the transition elements. The two rows of 14 elements at the bottom of the periodic are the lanthanides and actinides.

11. Periodic Table 1 2 3 4 5 6 7 Li 3 He 2 C6C6 N7N7 O8O8 F9F9 Ne 10 Na 11 B5B5 Be 4 H1H1 Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 Cs 55 Ba 56 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86 Fr 87 Ra 88 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 Mg 12 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er 68 Tm 69 Yb 70 Lu 71 Th 90 Pa 91 U 92 Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 Lr 103 La 57 Ac 89 1 2 3 4 5 6 7 1 2 Alkali metals Alkaline earth metals Transition metals Boron group Halogens Noble gases 3 56781112 1314151617 18 4 Lanthanide Series 6 7 Actinide Series C Solid Br Liquid H Gas 11 gases at room temperature 2 liquids at room temperature 25 Synthetic elements Groups tell you the number of valence e - Periods tell you the number of energy levels/orbitals. 910 Nonmetals