2.1.2 Noble Gases

2.1 Chemical Compounds [5 class periods] 1. Relate the stability of Noble Gases to having a full outer shell of electrons 1. Know uses of helium and argon related to their chemical unreactivity. 1. Understand bonding and valency in terms of the attainment of a stable electronic structure. 2. Know the Octet rule and its limitations 3. Predict simple chemical formulae of the first 36 elements (excluding d-block elements) 3. Predict the formulae of hydroxides, carbonates, nitrates, hydrogencarbonates, sulfites and sulfates of these elements (where such exist). 3. Realise that transition elements (Cu, Fe, Cr and Mn only) show Variable Valency

Discovered He 1868 Ar 1894 Ne, Kr and Xe in 1898 Rn 1900 Unreactive because they have a full outer shell of electrons

Uses Helium used in airships as it is lighter than air Not as light as hydrogen [twice as heavy per volume] but does not burn [Hindenberg] Used in making the atmosphere of deep sea divers as it is less likely to cause the “bends” – It gives the diver a “Mickey Mouse” voice because it has such a low density compared to air.

Argon The most common Noble Gas. Used to fill normal incandescent light bulbs to stop them imploding, to reduce evaporation of the filament and because it is unreactive Used as inert atmosphere for welding

All atoms are trying to get structure of nearest Noble Gas i.e. eight electrons in their outer shell and thus stability

Trends in Noble gases Noble gases don’t react in general because they have a full outer shell. As one goes down the Group the molecules are larger Makes it easier to form temporary dipoles due to larger electron clouds So van der Waal’s forces are greater More energy required to break these. So MP and BP get higher Same trend in halogens