55
Cs
132.905
Cesium
Alkali Metal
Group 1
Period 6
Block s
Cesium is a chemical element of the periodic table with chemical symbol Cs and atomic number 55 with an atomic weight of 132.905 u and is classed as alkali metal and is part of group 1 (alkali metal). Cesium is solid at room temperature.
Cesium in the periodic table
| Symbol | Cs |
| Atomic number | 55 |
| Group | 1 (Alkali metal) |
| Period | 6 |
| Block | s |
| Classification | Alkali Metal |
| Appearance | Silvery gold |
| Color | Silver |
| Number of protons | 55 p+ |
| Number of neutrons | 78 n0 |
| Number of electrons | 55 e- |
From Wikipedia, the free encyclopediaCaesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium.
Physical properties
| Phase at STP | Solid |
| Density | 1.93 g/cm3 |
| Atomic weight | 132.905 u |
Thermal properties
| Melting point | 301.7 K 28.55 °C 83.39 °F |
| Boiling point | 944 K 670.85 °C 1239.53 °F |
| Heat of vaporization | 67.74 kJ/mol |
Atomic properties
| Electronegativity (Pauling Scale) | 0.79 |
| Electron affinity | 45.505 kJ/mol |
| Oxidation states | −1, +1 (a strongly basic oxide) |
| Ionization energies |
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Electron configuration for cesium
Electron configuration Shorthand configuration | [Xe] 6s1 | ||||||||||||||||||||||||||||||||||||||||
| Full configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s1 | ||||||||||||||||||||||||||||||||||||||||
Electron configuration chart |
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| Electrons per shell | 2, 8, 18, 18, 8, 1 | ||||||||||||||||||||||||||||||||||||||||
| Valence electrons | 1 | ||||||||||||||||||||||||||||||||||||||||
| Valency electrons | 1 | ||||||||||||||||||||||||||||||||||||||||
| Bohr model | Figure: Shell diagram of Cesium (Cs) atom. | ||||||||||||||||||||||||||||||||||||||||
Orbital Diagram |
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The history of Cesium
| Discovery | Robert Bunsen, Gustav Kirchhoff (1860) |
| First isolation | Carl Setterberg (1882) |
Discovery of cesium In 1860, German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium in the mineral water from Dürkheim, Germany. Because of the bright blue lines in the emission spectrum, they derived the name from the Latin word caesius, meaning sky-blue. Caesium was the first element to be discovered with a spectroscope, which had been invented by Bunsen and Kirchhoff only a year previously. In 1967, acting on Einstein's proof that the speed of light is the most-constant dimension in the universe, the International System of Units used two specific wave counts from an emission spectrum of caesium-133 to co-define the second and the metre. Since then, caesium has been widely used in highly accurate atomic clocks. | |
| Original word | caesius |
| Language of origin | Latin |
| Name source | Properties |
| Meaning | “Sky blue” |
Naming The name is derived from the Latin 'caesius', meaning sky-blue, after the two bright blue spectral lines that revealed the new element. | |