Symbol: Cs
Atomic Number: 55
Atomic Weight: 132.90543
Element Classification: Alkali Metal
Discovered By: Gustov Kirchoff, Robert Bunsen
Discovery Date: 1860 (Germany)
Name Origin: Latin: coesius (sky blue); for the blue lines of its spectrum.

Density (g/cc): 1.873
Melting Point (K): 301.6
Boiling Point (K): 951.6
Appearance: Very soft, ductile, light gray metal
Atomic Radius (pm): 267
Atomic Volume (cc/mol): 70.0
Covalent Radius (pm): 235
Ionic Radius: 167 (+1e)
Specific Heat (@20C J/g mol): 0.241
Fusion Heat (kJ/mol): 2.09
Evaporation Heat (kJ/mol): 68.3
Thermal Conductivity (@25C W/m K):
Debye Temperature (K): n/a
Pauling Negativity Number: 0.79
First Ionizing Energy (kJ/mol): 375.5
Oxidation States: 1
Electronic Configuration: [Xe] 6s1
Lattice Structure: Body-Centered Cubic (BCC)
Lattice Constant (): 6.050
Lattice C/A Ratio: n/a

Mineral Hardness [no units]: 0.2
Brinell Hardness [/MN m-2]: 0.14

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