GCSE-IGCSE-KS4 Revision Notes Group 0 The Noble Gases at Doc Brown's Chemistry Clinic. teaching summary diagram diagrams revise revision notes questions question worksheet worksheets quiz quizzes revising for science examinations docbnoble

Keywords * argon uses * compounds * data on elements * electron arrangement * helium uses * introduction * krypton uses * neon uses * radon dangers * xenon uses * uses of noble gases * extra information

m/c QUIZ on Noble Gases * EMAIL query?comment * Multi-word fill worksheet

Note: Using 0 to denote the Group number of Noble Gases is very historic now since compounds of xenon known exhibiting a valency of 8. Because of the horizontal series of elements e.g. like the Sc to Zn block (10 elements), Groups 3 to 7 can also be numbered as Groups 13 to 17, and Group 0 numbered Group 18, to fit in with the actual number of vertical columns of elements. This can make things confusing, but there it is, classification is still in progress!

Periodic Table

Introduction to the Group 0/8 Noble Gases

(see data table below)

The "Noble Gases" are the last group in the Periodic Table i.e. they form the last elements at the end of a period.
They are all non-metallic elements and all are colourless gases at room temperature and pressure with very low melting points and boiling points.
They form 1% of air, and most of this is argon. All the noble gases, except radon, are separated by the fractional distillation of liquified air. Helium can also be obtained from natural gas wells where it has accumulated from radioactive decay (alpha particles become atoms of helium gas when they gain two electrons).
They are very unreactive elements because the highest occupied electron level is complete, meaning they have a full shell of outer electrons! (see diagrams below). They have no 'wish' electronically to share electrons to form a covalent bond or to lose or gain electrons to form an ionic bond. In other words, they are electronically very stable.
They exist as single atoms, that is they are monatomic He Ne Ar etc. (NOT diatomic molecules as with many other gases - reasons given above). This is because of their electronic stability - see point above and diagrams below.
Their very inertness is an important feature of their practical uses.
Down the Group with increasing atomic number ...
- the melting point and boiling point steadily increase (see data)
- the density steadily increases (see data)
- more likely to react and form a compound with very reactive elements like fluorine eg
  - Stable compounds of xenon are now known and synthesised BUT not before 1961!

Selected data on the Group 0/8 Noble Gases (more AS-A2 data)
Chemical symbol and name	Atomic number	Electron arrangement	Melting point	Boiling point	Atomic radius pm (10^-12m)
He helium	2	2	-272^oC , 1K	-269^oC , 4K	49
Ne neon	10	2.8	-249^oC , 24K	-246^oC , 27K	51
Ar argon	18	2.8.8	-189^oC , 84K	-186^oC , 87K	94
Kr krypton	36	2.8.18.8	-157^oC , 116K	-152^oC , 121K	109
Xe xenon	54	2.8.18.18.8	-112^oC , 161K	-108^oC , 165K	130
Rn radon	86	2.8.18.32.18.8	-71^oC , 202K	-62^oC , 211K	136

Uses of the the Group 0/8 Noble Gases
He helium		The gas is much less dense than air (lighter) and is used in balloons and 'airships'. Because of its inertness it doesn't burn in air UNLIKE hydrogen which used to be used in large balloons with 'flammable' consequences e.g. like the R101 airship disaster! Helium is also used in gas mixtures for deep-sea divers.
Ne neon	just like this website!	Neon gives out light when high voltage electricity is passed through it, so its used in glowing 'neon' advertising signs and fluorescent lights.
Ar argon		Argon, like all the Noble Gases is chemically inert. It used in filament bulbs because the metal filament will not burn in Argon and it reduces evaporation of the metal filament. It is also used to produce an inert atmosphere in high temperature metallurgical processes, eg in welding where it reduces brittle oxide formation reducing the weld quality. Its bubbles are used to stir mixtures in steel production. Argon is the cheapest to produce.
Kr krypton		Not used by superman! BUT is used in fluorescent bulbs, flash bulbs and laser beams.
Xe xenon		Good for winning scrabble games! AND also used in fluorescent bulbs, flash bulbs and lasers.
Rn radon		This has almost no uses, but does have dangers! Radio-isotopes of radon are produced by radioactive decay of heavy metals (e.g. uranium) in the ground. Can build up in cellars. Like all radio-isotopes it can cause cell damage (DNA) and ultimately cancer (see link below). However it is used in some forms of cancer treatment

Extra 'bits and bobs' on THE NOBLE GASES
% in Air by volume	0.0005% He, 0.0018% Ne, 0.93% Ar, 0.0001% Kr, 0.00001% Xe, ?% Rn - impossible to be zero, but an extremely minute trace hopefully! (varies with local geology)
Radon dangers	Rocks, e.g. granite, can contain uranium metal compounds which are radioactive. When they 'decay' radioactively, radioactive and harmful radon gas can be formed.
Compounds of Noble Gases - yes they do exist!	From the early 1960's compounds have been made, but only xenon compounds are stable and usually combined with oxygen and fluorine, which, not surprisingly, are the more reactive non-metals e.g. Xe + 2F₂ => XeF₄ (using Ni catalyst 60^oC, easy if you know how! and another catalytic bonus from a transition metal!)

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