Number 99
Einsteinium is a chemical element with atomic number 99 and sits in Group ‘Actinides’ and Period 7 on the periodic table. It is named after the renowned physicist Albert Einstein.
It is an actinide with a stable oxidation state of +3 in both solids and aqueous solutions. It is the only actinide to exist in divalent form and its properties resemble those of its immediate neighbours.
Isotopes
There are 16 known isotopes of einsteinium with mass numbers ranging from 241 to 256. The most stable isotope, einsteinium-252, has a half-life of 471.7 days. It decays into berkelium-248 through alpha decay or into californium-252 through electron capture.
Formation of Isotopes
A transuranic actinide, Einsteinium is formed from uranium and thorium by the absorption of multiple neutrons. This process requires a large energy source. Hence, it is synthesized synthetically in nuclear reactors.
Isotopes are forms of an atom that differ by the total number of nucleons present in the centre (N+Z = A). Isotopes also have different ionization energies and electron affinities.
Einsteinium’s ionization energy is 6.42 eV which indicates that it has a low ionization affinity and a high probability of gaining an electron when bombarded with a negative ion in the gaseous phase.
Electronegativity of Einsteinium is 1.3 which shows that it has a tendency to attract more electrons than other atoms or molecules. This is the most important property for determining its stability and reducing the chances of forming ions.
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