Page 21 - Curriculum Visions Dynamic Book

K see Potassium Krypton (Kr)
Element 36. One of the noble gases in group 8 in the Periodic Table.
It is an inert gas and forms very few compounds.
Krypton is heavier than air, colourless, odourless and tasteless. It produces brilliant green and orange lines in a spectroscope (an instrument for finding the natural colours emitted from an element).The fundamental unit of length, the metre, is defined
as 1m = 1,650,763.73 wavelengths
of the orange–red line of krypton.
When a current of electricity is passed through a glass tube containing krypton at low pressure, it gives out a bluish-white light.
Discovery
Krypton was discovered in 1898 by the British chemists Sir William Ramsay and Morris W.Travers in the liquid that remained after liquid air had nearly boiled away.
Technology
Krypton can be used on its own
or with argon and neon as the gas
in incandescent (ordinary) bulbs. Electric-discharge tubes filled with
krypton are used to light airfields
because the red light they give out
can be seen from far away and also penetrates fog and haze better than
ordinary light. Krypton is used in some types of fluorescent lamps and for flash lamps used in high-speed photography. However, it is not widely used because of its high cost of production.
Geology
Krypton is found in the air in about one part per million. It is also found in the atmosphere of Mars.
Biology
Krypton is not found in living things, but since it is inert, it is not harmful.
21
Key facts...
Name: krypton
Symbol: Kr
Atomic number: 36
Atomic weight: 83.80
Position in Periodic Table: group 8 (18)
(noble gases); period 4
State at room temperature: gas Colour: colourless
Density of gas ay 20°C: 3.48 g/cc Melting point: –157°C
Boiling point: –152°C
Origin of name: from the Greek word
kryptos, meaning hidden
Shell pattern of electrons: 2–8–18–8
For more on krypton, see Volume 1: Hydrogen and the Noble Gases in the Elements set.