Here's a definition of radioactive elements and as well as the list of common radioactive elements.

2. Radioactive elements are
elements that have an
unstable nucleus. When the
nuclei are considered
unstable they radiate
alpha, beta, and gamma
radiation and is converted
into a stable element.
Elements are considered
radioactive if they are

3. Luminous watch
Smoke detector X-ray
Uranium glass/ Vaseline glass Ceramics Glass lantern mantle

4. HYDROGEN (H)
Atomic number 1
Atomic mass number 3
Decay type Beta Decay (β-)
Half life 12 years

5. RADIUM (Ra)
Atomic number 88
Atomic mass number 225
Decay type Beta Decay (β-)
Half life 15 days

6. Radium (Ra)
Atomic number 88
Atomic mass number 224
Decay type Alpha
Half life 4 days

7. Uranium (U)
Radioacti Atomic Atomic Decay Half life
ve number mass type
element number
Uranium 92 233 Alpha 162,000
(U) years
Uranium 92 234 Alpha 248,000
(U) years
Uranium 92 235 Alpha 713
(U) million
years
Uranium 92 236 Alpha 23.9
(U) million
years
Uranium 92 238 Alpha 4.51

8. Polonium (Po)
Atomic number 84
Atomic mass number 210
Decay type Alpha
Half life 138 days

9. Carbon (C)
Atomic number 6
Atomic mass number 14
Decay type Beta Decay (β-)
Half life 5,730 years

10. Technetium (Tc)
Atomic number 43
Atomic mass number 99
Decay type Beta Decay (β-),
Gamma
Half life 210,000 years

11. Iodine (I)
Radioac Atomic Atomic Decay Half
tive number mass type life
elemen numbe
t r
Iodine (I) 53 129 Beta Decay 17.2 million
(β-), Gamma years
Iodine (I)v 53 131 Beta Decay 8 days
(β-), Gamma
Iodine (I) 53 134 Beta Decay 52 minutes
(β-), Gamma

12. Lead (Pb)
Atomic number 82
Atomic mass number 210
Decay type Beta Decay (β-),
Gamma
Half life 21 years

13. Cesium (Cs) 134 &
137
Atomic number 55
Atomic mass number 134,
137
Decay type Beta Decay (β-),
Gamma
Half life 2 years, 30 years

14. Plutonium (Pu)
239
Atomic number 94
Atomic mass number 239
Decay type Alpha
Half life 24,390 years