55 - Cesium alkali metal
Discovered by Robert Bunsen in 1860
Caesium 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.
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
57-71 La-Lu Lanthanides
89-103 Ac-Lr Actinides
| Shell | Electrons | Orbitals |
|---|---|---|
| 1 | 2 | 2 in 1s |
| 2 | 8 | 2 in 2s + 6 in 2p |
| 3 | 18 | 2 in 3s + 6 in 3p + 10 in 3d |
| 4 | 18 | 2 in 4s + 6 in 4p + 10 in 4d |
| 5 | 8 | 2 in 5s + 6 in 5p |
| 6 | 1 | 1 in 6s |
133 u Atomic Mass
3.3 Å Atomic Radius
944 K Boiling Point
2.44 Å Covalent Radius
1.93 g/cm³ Density
45.5 Electron Affinity
0.79 Electronegativity
3.89 eV First Ionization Energy
302 K Melting Point
6 Number of Shells
1 Electron Valency
55 Atomic Number
2, 8, 18, 18, 8, 1 Electron Shell Occupations
0.242 J/(g K) Specific Heat