1. 12345678 910111213141516 1718192021222324 2526272829303132 3334353637383940 4142434445464748 4950515253545556 5758596061626364

2. Dmitri Mendeleev Return

3. The tendency to recur at regular intervals Return

4. The physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number Return

5. period Return

6. Group or family Return

7. Alkali metals Return

8. H, Li, Na, K, Rb, Cs, Fr Return

9. Li, Na, K, Rb, Cs, Fr Return

10. 1

11. Alkaline earth metals Return

12. 1

13. 2

14. 2

15. Be, Mg, Ca, Sr, Ba, Ra Return

16. Alkaline earth metals Return

17. Alkali metals Return

18. halogens Return

19. F, Cl, Br, I, At Return

20. 7

21. halogens Return

22. 18 Return

23. 17 Return

24. He, Ne, Ar, Kr, Xe, Rn Return

25. solid Return

26. Br and Hg Return

27. H, N, O, F, He, Cl, Ne, At, Kr, Xe, Rn Return

28. metals Return

29. metals Return

30. B, Si, Ge, As, Sb, Te, Po, At Return

31. B

32. Ne Return

33. Inner transition elements Return

34. 7

35. 8

36. Cl Return

37. Mg Return

38. Al Return

39. P

40. K

41. Ca Return

42. Po or As Return

43. F

44. 2

45. 5

46. 3

47. 2

48. Ca Return

49. S

50. K

51. As Return

52. Ga Return

53. Mg Return

54. H

55. Cl Return

56. H

57. 4

58. 8

59. Be Return

60. F

61. Na Return

62. Si Return

63. S

64. Be Return

65. 7