Noble Gases


Doc Brown's Chemistry KS4 Science GCSE/IGCSE/O Level Chemistry Revision Notes

The GROUP 0 (8/18) Noble Gases of the Periodic Table

 The Group 0 elements, the NOBLE GASES consist of helium, neon, argon, krypton, xenon and radioactive radon. The chemical inertness of the noble gases is explained. The physical properties of the noble gases are described and the group trends of noble gases in terms of melting points, boiling points, density, chemical reactivity and atomic radii. The 'few' chemical properties of some noble gases e.g. xenon are mentioned. The uses of noble gases are also described and explained. These revision notes on noble gases should prove useful for the new AQA, Edexcel and OCR GCSE (91) chemistry science courses.

Keywords and phrases for Group 0 Noble Gases * argon uses * compounds * data on elements * electron arrangement * helium uses * introduction * krypton uses * neon uses * radon dangers * xenon uses * the uses of noble gases * extra information

GCSE m/c QUIZ on Noble Gases * (c) doc b Multi-word fill worksheet on the Noble Gases

Advanced Level Students GCE AS/A2/IB Advanced Level Chemistry Notes on the Group 0/18 Noble Gases

BUT reading this page reminds you of what you theoretically leaned from GCSE/IGCSE/O Level courses on noble gases!

So this page can act as a primer for the study of noble gases helium, neon, argon, krypton, xenon


Where are the Group 0 Noble Gases in the Periodic Table?

Periodic Table

The Group 0 Noble Gases form the last vertical column on the right of the Periodic Table, where you find most of the non-metallic elements. Therefore the Noble Gas is the last element on ANY complete period. At the bottom of Group 0 is radioactive noble gas element radon (Rn) which is not shown.

Note: The group number for 1 to 7  is equal to the maximum valency of the element (except for O and F). Using 0 to denote the Group number of Noble Gases is very historic since no compounds of Noble Gases where known until the 1960s. Now, since compounds of xenon exhibiting a valency of up to 8 have been synthesised. 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 can be 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!



Introduction to the Group 0 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, the final vertical column of elements in the periodic table.

    • In descending order, the six noble gases are ...

      • helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).

      • They were called noble 'gases' because they were so unreactive (the same reasons unreactive metals like gold are sometimes referred to as a 'noble metal').

  • Noble gases form the last element of a any period, with a full outer electron shell. This outer electron similarity of the noble gases makes them behave in a chemically similar e.g. the least reactive of any elements and is a modern pre-requisite of a set of elements belonging to the same group. BUT their similarity in physical properties and the chemical reactions now known (e.g. for xenon) fits in well with Mendeleev's original conception of a group classification even though he had no idea they existed !

  • The noble gases are all non-metallic elements and all are colourless gases at room temperature and pressure with very low melting points and boiling points.

  • The noble gases form 1% of air, and most of this is argon. All the noble gases, except radioactive 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 alpha decay (alpha particles become atoms of helium gas when they gain two electrons).

    • (c) doc b alpha particle decay of the radioisotope uranium-235

    • Many of the unstable nuclei of heavier atoms (high proton/atomic number) decay by alpha emission. The alpha particle (helium nucleus of 2 protons + 2 neutrons) grabs 2 electrons to form a stable atom of helium gas.

  • The electronic structure of the noble gases is the basis for explaining why they are so unreactive.

  • The noble gases are very unreactive elements because the highest occupied electron level is complete, meaning they have a full shell of outer electrons! (see diagrams below).

    • Helium has a full outer shell of 2 electrons, and the rest of the noble gases - neon, argon, xenon etc. all have a full outer shell of 8 electrons, giving them great electronic stability and chemical stability .

    • The group 0 noble gases are the least reactive elements in the whole of the periodic table.

    • They have no great '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 are sometimes referred to as inert gases, because of their lack of chemical reactivity.

    • In fact their lack of reactivity was one reason why they were some of the last naturally occurring elements of the periodic table to be discovered.

      • They were discovered because the density of chemically made nitrogen was different from the nitrogen obtained from air after removal of oxygen.

      • Therefore it was reasoned that there must be some 'unknown' gases in air.

      • With improved technology in the early 20th century, careful low temperature fractional distillation of liquified air revealed fractions containing noble gases, and this is how they are usually obtained in industry.

  • The noble gases exist as single atoms, that is they are 'monatomic molecules' He Ne Ar etc. (NOT diatomic molecules as with many other gases like oxygen O2 and nitrogen N2 - reasons given above). This is because of their electronic stability - see point above and diagrams below.

  • The very inertness of the noble gases is an important feature of their practical uses

  • Important group 0 noble gas trends to know ...

  • ... down the Group 0 noble gases with increasing atomic number for the Noble Gas elements ...

    • ... the melting point and boiling point of noble gases steadily increase down the group (see data) because the weak intermolecular forces increase with the size of the atom.

      • This is because of the increase in the number of electrons, due to an extra electron shell from one noble gas down to the next one down the group on the next period.

      • This trend produces an increasingly larger atom, which results in an increase in the weak electrical attractive forces between the noble gas atoms (increasing intermolecular forces/intermolecular bonding).

      • So, because the strength of the intermolecular forces or intermolecular bonding forces between the atoms increases, so more energy (higher kinetic energy, higher temperature) is needed to boil the condensed Noble Gas and overcome these attractive forces.

    • ... the density of noble gases steadily increases down the group (see data)

    • ... down the group, theoretically, the noble gases are more likely to react and form a compound with very reactive elements like fluorine, this because the outer electrons are increasingly less strongly held giving a greater chance of electron sharing in forming a covalent bond with other very reactive non-metals like fluorine, chlorine and oxygen e.g.

      • Stable compounds of xenon, like xenon tetrafluoride, are now known and synthesised BUT not before 1961!

      • The most reactive Noble Gas would be radon BUT this is a highly dangerous radioactive gas!

      • Some VERY unstable compounds have been made from argon and krypton.

      • The reason for the lack of reactivity by noble gases is explained in the box below.



Electron structure and reactivity of noble gases

The electron arrangement of the first 3 Noble Gases with full very stable outer shells (are shown) making the noble gas elements VERY unreactive. Because the noble gas atoms have a full, and very stable, outer electron shell, they are very reluctant to share electrons to form a covalent bond OR lose/gain electrons to form an ion and ionic bond. As the atom gets bigger, the outer electrons are less strongly held and the lower member noble gases e.g. xenon can be tempted into chemically reacting with VERY reactive chemical reagents like fluorine (the most reactive non-metal).

Noble Gases Noble Gases Noble Gases


Selected data on the Group 0 Noble Gases (more advanced data)

Chemical symbol & name

Atomic number Electron arrangement Melting point Boiling point Density g/cm3 Atomic radius pm (picometre) and nm (nanometres)
He helium 2 2 -272oC , 1K -269oC , 4K 0.0002 49 and 0.049
Ne neon 10 2.8 -249oC , 24K -246oC , 27K 0.0008 51 and 0.051
Ar argon 18 2.8.8 -189oC , 84K -186oC , 87K 0.0018 94 and 0.094
Kr krypton 36 -157oC , 116K -152oC , 121K 0.0037 109 and 0.109
Xe xenon 54 -112oC , 161K -108oC , 165K 0.0059 130 and 0.130
Rn radon 86 -71oC , 202K -62oC , 211K 0.0097 136 and 0.136




Proton number of group 0 noble gases



All group 0 noble gases have eight electrons in the full outer shell, except helium just has the two, but still a full shell!


The melting point of group 0 noble gases increases down the group.



The boiling point of group 0 noble gases increases down the group.


The density of group 0 noble gases increases down the group.


The atomic radii of group 0 noble gases increase down the group.



Note: For atomic radii: 1nm = 109m,  1pm = 1012m,  nm x 1000 = pm,  nm = pm/1000

Atomic radii always increase down a group with increase in atomic number because extra electron shells are successively added.


 Uses of the Group 0/8 Noble Gases

The noble gases are non-flammable and chemically very unreactive and this chemical inertness is an important characteristic when understanding the uses and applications of noble gases and sometimes the low density is important too.

Uses of He helium The noble gas helium gas is much less dense than air (lighter) and is used in party balloons and 'airships' because it 'floats' in air! Thanks Niamh, (aged 31/2 at the time), for putting up with Granddad's camera work!

Another advantage is that because of its inertness, helium 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 respiration.

Liquid helium is used to achieve very low temperature in cryogenics technology.

Uses of Ne neon Noble Gasesjust like this website! The noble gas neon gives out 'white light' when high voltage electricity is passed through it, so neon is used in glowing 'neon' advertising signs and fluorescent lights. 
Uses of Ar argon Noble GasesNoble Gases The noble gas 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. Argon 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. Argon bubbles are used to stir mixtures in steel production. Argon is the cheapest noble gas to produce, it has the biggest % of any noble gas in air.
Uses of Kr krypton   The noble gas krypton is not used by superman! BUT krypton is used in fluorescent bulbs, flash bulbs and laser beams.
Uses of Xe xenon   The noble gas xenon is good for winning scrabble games! AND xenon also used in fluorescent bulbs, flash bulbs and lasers!
Rn radon Noble Gases The noble gas radon 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. Radon can build up in cellars, especially in granite areas (where cellars should be well ventilated to avoid dangerous concentrations building up) because it is a decay product of unstable uranium isotopes in the granite rocks. Like all radioisotopes, isotopes of radon can cause cell damage (DNA) and ultimately cancer (see link below) if breathed in. However it is used in some forms of cancer treatment, it always seems ironic that radioisotopes that cause cancer can also be used to kill cancer cells..




Extra 'bits and bobs' on THE NOBLE GASES

% noble gas 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 60oC, easy if you know how! and another catalytic bonus from a transition metal!)



Advanced Level Students GCE AS/A2/IB Advanced Level Chemistry Notes on the Group 0/18 Noble Gases

BUT reading this page reminds you of what you theoretically leaned from GCSE/IGCSE/O Level courses on noble gases!

So this page can act as a primer for the study of noble gases helium, neon, argon, krypton, xenon

KS4 Science Group 0 Noble Gases GCSE chemistry guide notes on Group 0 Noble Gases for schools colleges academies science course tutors images pictures diagrams of apparatus for Group 0 Noble Gases investigations word balanced symbol equations of Group 0 Noble Gases science chemistry revision notes on Group 0 Noble Gases revising the chemistry of Group 0 Noble Gases help in chemical understanding of Group 0 Noble Gases description of Group 0 Noble Gases experiments for chemistry courses university courses in chemistry careers in chemistry jobs in the chemical industry laboratory assistant apprenticeships in chemistry technical internship in chemistry IGCSE chemistry Group 0 Noble Gases Group 0 Noble Gases USA US grade 8 grade 9 grade10 Group 0 Noble Gas chemistry

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