Periodic Table – About.com Chemistry

This is an online interactive periodic table of the elements. Click on an element symbol in the periodic table to get facts for that element. Printable periodic tables and a list of elements by increasing atomic number are also available. 1 IA 1A 18 VIIIA 8A 1 H 1.008 2 IIA 2A 13 IIIA 3A 14 IVA 4A 15 VA 5A 16 VIA 6A 17 VIIA 7A 2 He 4.003 3 Li 6.941 4 Be 9.012 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.00 9 F 19.00 10 Ne 20.18 11 Na 22.99 12 Mg 24.31 3 IIIB 3B 4 IVB 4B 5 VB 5B 6 VIB 6B 7 VIIB 7B 8 9 VIII 8 10 11 IB 1B 12 IIB 2B 13 Al 26.98 14 Si 28.09 15 P 30.97 16 S 32.07 17 Cl 35.45 18 Ar 39.95 19 K 39.10 20 Ca 40.08 21 Sc 44.96 22 Ti 47.88 23 V 50.94 24 Cr 52.00 25 Mn 54.94 26 Fe 55.85 27 Co 58.47 28 Ni 58.69 29 Cu 63.55 30 Zn 65.39 31 Ga 69.72 32 Ge 72.59 33 As 74.92 34 Se 78.96 35 Br 79.90 36 Kr 83.80 37 Rb 85.47 38 Sr 87.62 39 Y 88.91 40 Zr 91.22 41 Nb 92.91 42 Mo 95.94 43 Tc (98) 44 Ru 101.1 45 Rh 102.9 46 Pd 106.4 47 Ag 107.9 48 Cd 112.4 49 In 114.8 50 Sn 118.7 51 Sb 121.8 52 Te 127.6 53 I 126.9 54 Xe 131.3 55 Cs 132.9 56 Ba 137.3 * 72 Hf 178.5 73 Ta 180.9 74 W 183.9 75 Re 186.2 76 Os 190.2 77 Ir 190.2 78 Pt 195.1 79 Au 197.0 80 Hg 200.5 81 Tl 204.4 82 Pb 207.2 83 Bi 209.0 84 Po (210) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra (226) ** 104 Rf (257) 105 Db (260) 106 Sg (263) 107 Bh (265) 108 Hs (265) 109 Mt (266) 110 Ds (271) 111 Rg (272) 112Cn (277) 113 Uut -- 114 Fl (296) 115 Uup -- 116 Lv (298) 117 Uus -- 118 Uuo -- * Lanthanide Series 57 La 138.9 58 Ce 140.1 59 Pr 140.9 60 Nd 144.2 61 Pm (147) 62 Sm 150.4 63 Eu 152.0 64 Gd 157.3 65 Tb 158.9 66 Dy 162.5 67 Ho 164.9 68 Er 167.3 69 Tm 168.9 70 Yb 173.0 71 Lu 175.0 ** Actinide Series 89 Ac (227) 90 Th 232.0 91 Pa (231) 92 U (238) 93 Np (237) 94 Pu (242) 95 Am (243) 96 Cm (247) 97 Bk (247) 98 Cf (249) 99 Es (254) 100 Fm (253) 101 Md (256) 102 No (254) 103 Lr (257)

Introduction to the Periodic Table

People have known about elements like carbon and gold since ancient time. The elements couldn't be changed using any chemical method. If you examine samples of iron and silver, you can't tell how many protons the atoms have. However, you can tell the elements apart because they have different properties. You might notice there are more similarities between iron and silver than between iron and oxygen. This is where the periodic table becomes useful. It organizes elements according to trends so that you can see the relationships between them.

What is the Periodic Table?

Dmitri Mendeleev was the first scientist to create a periodic table of the elements similar to the one we use today. You can see Mendeleev's original table (1869). This table showed that when the elements were ordered by increasing atomic weight, a pattern appeared where properties of the elements repeated periodically. This periodic table is a chart that groups the elements according to their similar properties. Mendeleev's table didn't have many elements. He had question marks and spaces between elements where he predicted undiscovered elements would fit.

Why was the Periodic Table Created?

Many elements remained to be discovered in Mendeleev's time. The periodic table helped predict the properties of new elements. The modern periodic table is used to predict properties and reactions of the elements.

Discovering Elements

The number of protons determines the atomic number of an element, which is its number on the periodic table. There aren't any skipped atomicnumbers on the modern periodic table because new elements are synthesized rather than discovered. The placement of these new elements on the periodic table can be used to help predict the element's properties.

Element Properties and Trends

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Periodic Table - About.com Chemistry