89 Ac (Actinium)
Appearance: Soft, Silvery-white, glows in the dark with a pale blue light because intense radioactivity exicites the air around it; sometimes with a golden cast
Mass number: 227
Atomic weight: 227.0278 g/mol
Atomic number(Z): 89
Electrons: 89
Protons: 89
Neutrons: 138
Group: 3
Period: 7
Block: d
Element category: Actinide
Electrons per shell: K2, L8, M18, N32, O18, P9, Q2
Electron configuration: 1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p66d17s2
Phase: Solid
Melting point: 1500 K(1227 oC)
Boiling point: 3500±300 K (3227±300 oC)
Density: 10 g/cm3
Molar volume: 0.000022542 m3/mol
Thermal conductivity: 12 W/m∙K
Half Life(s): 687060000
Lifetime(s): 991210000
Decay mode: β decay
Neutron cross section (Barns): 810
Heat of fusion: 14 kJ/mol
Heat of vaporization: 400 kJ/mol
Molar heat capacity: 27.2 J/(mol∙K)
Oxidation states: 3, 2
Ion charge: Ac4+
Electronegativity: 1.1
Valence: 3
Ionization energies: 1st: 499 kJ/mol 2nd: 1170 kJ/mol 3rd: 1900 kJ/mol
Covalent radius: 215 pm
Crystal structure: Face centered cubic
Thermal conductivity: 12 W/(m∙K)
CAS Number: 7440-34-8
Discovery & 1st isolation: Friedrich Oskar Giesel (1902)
Named: After Greek word ‘Actinos’ (means a ray) by André-Louis Debierne (1899)
Isotopes: 225Ac 226Ac 227Ac
Uses: Actinium is a very powerful source of α rays, but is rarely used outside research.
Biological role: It is toxic due to its radioactivity.
Natural abundance: Actinium is made by the neutron bombardment of radium-226. It is also occurs naturally in uranium ores
#actinium
