Page 39 - Curriculum Visions Dynamic Book

Cesium (Cs)
Element 55. Also caesium. It is a silvery- white alkali metal.
A member of group 1 in the Periodic Table, it is an extremely soft metal.
Cesium is the most alkaline element. It reacts explosively with cold water and even reacts with ice. It readily combines with oxygen. It also easily loses electrons when struck by light.
It is liquid close to room temperature, a property it shares with only gallium and mercury.
Discovery
It was discovered using a spectrometer in 1860 by Robert Bunsen and Gustav Kirchhoff in samples of mineral water from Durkheim, Germany. The clue was the distinctive pair
of blue lines they saw.
Technology
Because it easily loses electrons when struck by light, it is used for photoelectric cells. Cesium also goes into atomic clocks. One kg of cesium in outer space could propel
a vehicle 140 times as far as can be achieved by burning the same amount of any known liquid or solid. However, it cannot be used this way on Earth.
Geology
It is found in the mineral pollucite, an aluminosilicate. It also appears in rhodizite, a boron mineral.
Biology
Cesium is not found in living things and is rare. It may have the same effects on the body as potassium.
Key facts...
Name: caesium
Symbol: Cs
Atomic number: 55
Atomic weight: 132.9
Position in Periodic Table: group 1 (1) (alkali
metal); period 6
State at room temperature: solid (but melts
only slightly above this temperature) Colour: silvery-white
Density of solid: 1.87 g/cc
Melting point: 28.44°C
Boiling point: 671°C
Origin of name: named from the Latin caesius,
meaning sky-blue. It produces two bright lines in the blue part of the spectrum when it is analysed with a piece of chemical equipment called a mass spectrometer.
Shell pattern of electrons: 2–8–18–18–8–1
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