Editing Gadolinium (section)

===Isotopes===
{{Main|Isotopes of gadolinium}}
Naturally occurring gadolinium is composed of six stable isotopes, <sup>154</sup>Gd, <sup>155</sup>Gd, <sup>156</sup>Gd, <sup>157</sup>Gd, <sup>158</sup>Gd and <sup>160</sup>Gd, and one [[radioisotope]], <sup>152</sup>Gd, with the isotope <sup>158</sup>Gd being the most abundant (24.8% [[natural abundance]]). The predicted double beta decay of <sup>160</sup>Gd has never been observed (an experimental lower limit on its [[half-life]] of more than 1.3×10<sup>21</sup> years has been measured<ref name="DBD">{{Cite journal |last1=Danevich |first1=F. A. |last2=Kobychev |first2=V. V. |last3=Ponkratenko |first3=O. A. |last4=Tretyak |first4=V. I. |last5=Zdesenko |first5=Yu. G. |date=2001-11-05 |title=Quest for double beta decay of 160Gd and Ce isotopes |url=https://www.sciencedirect.com/science/article/pii/S0375947401009836 |journal=Nuclear Physics A |volume=694 |issue=1 |pages=375–391 |doi=10.1016/S0375-9474(01)00983-6 |issn=0375-9474|arxiv=nucl-ex/0011020 }}</ref>).

Thirty-three radioisotopes of gadolinium have been observed, with the most stable being <sup>152</sup>Gd (naturally occurring), with a half-life of about 1.08×10<sup>14</sup> years, and <sup>150</sup>Gd, with a half-life of 1.79×10<sup>6</sup> years. All of the remaining radioactive isotopes have half-lives of less than 75 years. The majority of these have half-lives of less than 25 seconds. Gadolinium isotopes have four metastable [[nuclear isomer|isomers]], with the most stable being <sup>143m</sup>Gd (''t''<sub>1/2</sub>= 110 seconds), <sup>145m</sup>Gd (''t''<sub>1/2</sub>= 85 seconds) and <sup>141m</sup>Gd (''t''<sub>1/2</sub>= 24.5 seconds).

The isotopes with [[atomic mass]]es lower than the most abundant stable isotope, <sup>158</sup>Gd, primarily decay by [[electron capture]] to isotopes of [[europium]]. At higher atomic masses, the primary [[decay mode]] is [[beta decay]], and the primary products are isotopes of [[terbium]].