99 Es (Einsteinium)
Appearance – Silvery; glows blue in the dark (Radioactive metal)
Mass number – 252
Atomic number (Z) – 99
Atomic weight – 252.0829 g/mol
Electrons: 99
Protons: 99
Neutrons: 153
Period – 7
Block – f
Element category – Actinide
Electrons per shell – K2, L8, M18, N32, O29, P8, Q2
Electron configuration – 1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p65f117s2
Phase – Solid
Melting point – 1133 k (860 oC)
Boiling point – 1269 k (996 oC)
Density – 8.84 g/cm3
Valence – 4
Half life(s) – 40750000
Lifetime(s) – 58800000
Oxidation states – 2, 3, 4
Electronegativity – Pauling scale: 1.3
Ionization energies – 1st: 619 kJ/mol
Decay mode – Alpha decay
Neutron cross section (Barns) – 160
Crystal structure – Face-centered cubic
Magnetic ordering – Paramagnetic
CAS Number – 7429-92-7
Naming – After Albert Einstein
Discovery – Lawrence Berkeley National Laboratory (1952)
Isotopes – 252Es 253Es 254Es 255Es
Uses – Einsteinium has no uses outside research.
Biological role – It is toxic due to its radioactivity
Natural Abundance – Einsteinium can be obtained in milligram quantities from the neutron bombardment of plutonium in a nuclear reactor
#Einsteinium
