Radioactivity: Spontaneous emission of particles or high-energy electromagnetic radiation from the nuclei of unstable atoms. 'Radiation' refers to the emissions, and 'radioactive source' refers to the source of the radiation.

 

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Radioactivity: Spontaneous emission of particles or high-energy electromagnetic radiation from the nuclei of unstable atoms. 'Radiation' refers to the emissions, and 'radioactive source' refers to the sour . . . View Full Definition

Thorium (Th): Atomic number: 90, Atomic mass: 232.04 g.mol -1, Electronegativity: 1.3, Density: 11.72 g.cm-3 at 20°C, Melting point: 1750 °C, Boiling point: 4790 °C, Vanderwaals radius: 0.182 nm, Ionic ra . . . View Full Definition

Technetium (Tc): Atomic number: 43, Atomic mass: (99) g.mol -1, Electronegativity: 1.9, Density: 11.5 g.cm-3 at 20°C, Melting point: 2200 oC, Boiling point: 4877 oC, Vanderwaals radius: 0.128 nm, Isotopes: 9 . . . View Full Definition

Protactinium (Pa): Atomic number: 91, Atomic mass: 231.0359 g.mol -1, Electronegativity: 1.5, Density: 15.37 g.cm-3 at 20°C, Melting point: 1600 °C, Boiling point: unknown, Vanderwaals radius: unknown, Ionic r . . . View Full Definition

Dysprosium (Dy): Atomic number: 66, Atomic mass: 162.50 g.mol -1, Electronegativity: 1.2, Density: 8.6 g.cm-3 at 20°C, Melting point: 1412 °C, Boiling point: 2562 °C, Vanderwaals radius: unknown, Ionic radiu . . . View Full Definition

Actinium (Ac): Atomic number: 89, Atomic mass: 227 g.mol -1, Electronegativity: 1.1, Density: 10.07 g.cm-3 at 20°C, Melting point: 1050 °C, Boiling point: 3250 °C, Vanderwaals radius: unknown, Ionic radius . . . View Full Definition