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Einsteinium is a synthetic chemical element; it has symbol Es and atomic number 99. It is named after Albert Einstein and is a member of the actinide series and the seventh transuranium element. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952.
Einsteinium (99 Es) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be discovered (in nuclear fallout from the Ivy Mike H-bomb test) was 253 Es in 1952. There are 18 known radioisotopes from 240 Es to 257 Es, and 4 nuclear isomers.
It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all elements that have been produced in amounts large enough to see with the naked eye (after einsteinium). It was named after the university and the U.S. state of California.
There are 20 isotopes of fermium listed in NUBASE 2016, [15] with atomic weights of 241 to 260, [b] of which 257 Fm is the longest-lived with a half-life of 100.5 days. 253 Fm has a half-life of 3 days, while 251 Fm of 5.3 h, 252 Fm of 25.4 h, 254 Fm of 3.2 h, 255 Fm of 20.1 h, and 256 Fm of 2.6 hours.
“Californium production campaigns are conducted every other year to produce from curium about 100 milligrams of californium-252, tens of milligrams of berkelium-249 and micrograms of einsteinium.
The s-block and p-block together are usually considered main-group elements, the d-block corresponds to the transition metals, and the f-block corresponds to the inner transition metals and encompasses nearly all of the lanthanides (like lanthanum, praseodymium and dysprosium) and the actinides (like actinium, uranium and einsteinium). The ...
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