Periodiska systemet (Mendelejevs schema) Grupp—>j Period— v 1 i a b II a b III a b IV a b V a b VI a b VII a b VIII a b x—Grupp Period V K 1 H 2 He K L 3 Li 4 Be 5 B 6 C 7 N 8 O 9 F 10 Ne : L M 11 Na 12 Mg 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar M N 19 K 29 Cu 20 Ca 30 Zn 21 Sc 31 Ga 22 Ti 32 Ge 23 V 33 As 24 Cr 34 Se 25 Mn 35 Br 26 Fe 27 Co 28 Ni 36 Kr N 0 37 Rb 47 Ag 38 Sr 48 Cd 39 Y 49 In 40 Zr 50 Sn 41 Nb 51 Sb 42 Mo 52 Te 43 Ma 53 J 44 Ru 45 Rh 46 Pd 54 X O P 55 Cs 79 Au 56 Ba 80 Hg 57—71* 81 TI 72 Hf 82 Pb 73 Ta 83 Bi 74 W 84 Po 75 Re 85 At 76 Os 77 Ir 78 Pt 86 Rn P Q 87 Fr 88 Ra 89 Ac 90 Th 91 Pa 92 U Q Periodiska systemet — 128 — Periodiska systemet *57 La Lantan 58 Ce Cerium 59 Pr Praseodym 60 Nd Neodym 61 II Illinium 62 Sm Samarium 63 Eu Europium 64 Gd Gadolinium 65 Tb Terbium 66 Dy Dysprosium 67 Ho Holmium 68 Er Erbium 69 Tu Tulium 70 Yb Ytterbium 71 Lu (Cp) Lutetium »De sällsynta jordmetallerna.»