There are stable and unstable atoms. Stable atoms remain the same forever. Radioactivity comes from unstable atoms having too much energy, breaking down and decaying. During this process new atoms are created.

Name Symbol Atomic Number Group Period
Actinium Ac 89 3 7
Americium Am 95 - 7
Astatine At 85 17 6
Berkelium Bk 97 - 7
Bohrium Bh 107 7 7
Californium Cf 98 - 7
Curium Cm 96 - 7
Darmstadtium Ds 110 10 7
Dubnium Db 105 5 7
Einsteinium Es 99 - 7
Fermium Fm 100 - 7
Francium Fr 87 1 7
Hassium Hs 108 8 7
Lawrencium Lr 103 3 7
Meitnerium Mt 109 9 7
Mendelevium Md 101 - 7
Neptunium Np 93 - 7
Nobelium No 102 - 7
Plutonium Pu 94 - 7
Polonium Po 84 16 6
Promethium Pm 61 - 6
Protactinium Pa 91 - 7
Radium Ra 88 2 7
Radon Rn 86 18 6
Roentgenium Rg 111 11 7
Rutherfordium Rf 104 4 7
Seaborgium Sg 106 6 7
Technetium Tc 43 7 5
Thorium Th 90 - 7
Ununbium Uub 112 12 7
Ununhexium Uuh 116 16 7
Ununoctium Uuo 118 18 7
Ununpentium Uup 115 15 7
Ununquadium Uuq 114 14 7
Ununseptium Uus 117 17 7
Ununtrium Uut 113 13 7
Uranium U 92 - 7
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