Keychain Es Einsteinium.

<div> <strong> Atomic number <span class = "Apple-tab-span" style = "white-space: pre;"> </span>         99 </strong> </div> <div> <strong> Atomic mass           <span class = "Apple-tab-span" style = "white-space: pre;"> </span>252</strong></div> <div> <strong> Density, kg / m ? <span class = "Apple-tab-span" style = "white-space: pre;"> </span>         13500 </strong> </div> <div> <strong> Temperature</strong></div> <div> <strong> melting, ° С             860 </strong> </div> <div>   </div> <div>   </div> <p> Einsteinium is a radioactive, silvery metal. Einsteinium was discovered in December 1952. The element is named after Albert Einstein. Used to obtain mendelevium when bombarded in a cyclotron with helium nuclei. </p>