Cesium

Cesium is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28.5°C, making it one of only five elemental metals that are liquid at or near room temperature. Cesium is highly reactive and pyrophoric, reacting with water even at −116°C. It is used in atomic clocks, magnetometers, and as a promoter of catalysts for the hydrogenation of organic compounds.

Overview

English Name:

Cesium

Latin Name:

Caesium

Year Discovered:

1860

Discovered By:

Robert Bunsen, Gustav Kirchhoff

Group:

1

Period:

6

Electrons:

55

CAS Number:

7440-46-2

Cost Per 100 Grams:

$200

Atomic Properties

Electronic Configuration:

[Xe] 6s¹

Ion Charge:

+1

Ionisation Energies:

375.7 kJ/mol

Atomic Radius (Empirical):

265 pm

Atomic Radius (Calculated):

298 pm

Covalent Radius:

244 pm

Van Der Waals Radius:

343 pm

Ionisation Potential of An Atom:

3.89 eV

Electrons Per Layer:

2, 8, 18, 18, 8, 1

Atomic Multiplicities Of The Gas:

1

Atomic Weight:

132.91

Oxidation States

+1

Reactivity

Electron Affinity:

45.5 kJ/mol

Valence:

1

Electronegativity:

0.79

Thermal Properties

Melting Point:

28.44°C

Boiling Point:

678.1°C

Critical Point:

Pressure: N/A

Temperature: N/A

Thermal Conductivity:

35.9 W/(m·K)

Heat Capacity:

Specific: 0.242 J/(g·K)

Molar: 32.2 J/(mol·K)

Thermal Coefficient:

0.000078

Enthalpy:

Fusion: 2.06 kJ/mol

Vaporisation: 64.34 kJ/mol

Atomization: 178 kJ/mol

Curie Temperature:

N/A

Neel Temperature:

N/A

Superconductivity Point:

N/A

Physical and Chemical Properties

State of matter (25° C/ 77°F):

Solid

Density:

Solid: 1.93 g/cm³

Molar Volume (Vmol):

69.33 cm³/mol

Speed of Sound (Vs):

N/A

Hardness:

0.2

Bulk Modulus (K):

1.6 GPa

Shear Modulus (G):

N/A

Young's Modulus (E):

N/A

Color:

Silvery-gold

Brinell Hardness (MPa):

N/A

Liquid Density (Kg/m^3):

1.843 kg/m³

Hardness of Mohs:

0.2

Refractive Index:

N/A

Vickers Hardness (MPa):

N/A

Crystal Structure:

Body-centered cubic

Electromagnetic Properties

Electrical Type:

Conductor

Resistivity:

2.1 × 10^-7 Ω·m

Magnetic Type:

Paramagnetic

Superconductivity:

Not applicable

Volume Magnetic Susceptibility:

1.0 × 10^-5

Mass Magnetic Susceptibility:

5.2 × 10^-6 m³/kg

Molar Mass Susceptibility:

6.9 × 10^-4 m³/mol

Electrical Conductivity:

4.7 × 10^6 S/m

Mass (γmass):

1.0 × 10-25 kg

Mass (γmol):

1.0 × 10-22 mol

Volume (γvol):

69.33 L

Grid Parameters

Crystal Structure:

Body-centered cubic

Grid Parameters:

a = 6.08 Å

Attitude:

N/A

Debye Temperature:

N/A

Safety and Precautions

Signal Word:

Danger

Hazard Statements:

H250, H260, H314

Precautionary Statements:

P223, P231 + P232, P280, P305 + P351 + P338, P370 + P378

RTECS Number:

Not available

Risk:

Flammability: Pyrophoric
Health Risk: Corrosive
Reactivity: Reacts with water
Specific Risk: Reacts with air

Importance

Main sources:

Mining, processing

Main Usage:

Atomic clocks, magnetometers, catalysts

Nuclear Properties

Radioactive:

No

Isotopes:

Cs-133, Cs-135

Neutron Cross Sectional:

29 barns

Half Life (s):

None

Lifetime:

Stable

Prevalence

Universe:

0.00003%

Sun:

0.00003%

Oceans:

0.00000001%

Humans:

0.00000001%

Earth's Crust:

0.0003%

Meteorites:

0.0001%