Science / Chemistry / Pyrophoric: Catches fire spontaneously when exposed to air at normal room temperature. For example, powdered potassium metal is pyrophoric.
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Science / Periodic Table of Elements / 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 radius MORE
Science / Periodic Table of Elements / Praseodymium (Pr): Atomic number: 59 , Atomic mass: 140.91 g.mol -1, Electronegativity: 1.1, Density: 6.8 g.cm-3 at 20?°C, Melting point: 931 ?°C, Boiling point: 3512 ?°C, Vanderwaals radius: unknown, Ionic radius: 0 MORE