Since lead is a stable element, why doesn€™t the²³⁸U decay series shown in Fig. 43.7 stop at lead,²¹⁴Pb?

Fig.43.7

146 238U 4.47 x 10 y 145 234Th 144 24.10 d 143 234Pa 70s 142 234U 2.46 x 10 y 141 140 230TH 7.54 x 104 139 138 226Ra 1600 y 137 136 222Rn 3.82 d 135 134 218Po 3.10 m 133 a decay 214p 132 27 m | 214Bi 131 19.9 m 214Po 19.9 m B decay 130 210 T 129 1.637 x 10s 1.30 m 210Pb 22.3 y 128 210Bi 127 5.01 d 210Po 126 125 138.38 d 206Pb 124 80 81 82 83 84 85 86 87 88 89 90 91 92 93 Ac Th Pa U Np Hg TI Pb Bi Po At Rn Fr Ra