The Noble Gases and Halogens

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The Noble Gases and Halogens

This group contains helium, neon, krypton, xenon and radon.

The Noble Gases and Halogens

They are different to elements belonging to other groups due to their resistance to form compounds. The reason behind their unreactivity is their full outer shells that give stability to the atoms.

Properties:

Non-metals.

Gases.

Colourless.

Although they have similar properties they are not identical. For example, as you descend Group 0 the density of the gas increases as does the mass of a single atom.

Fluorine, chlorine, bromine and iodine make up the family of halogens. The last three being the most common. All the halogens exist as molecules, bonding covalently to their own atoms - adding stability as they complete their full outer shells.

Properties:

They all form coloured vapours:

Chlorine - green.

Bromine - red/brown.

Iodine - purple.

Melting points and boiling points are relatively low due to molecules been held together by weak inter-molecular forces. As you descend the group the melting and boiling point increases as the attraction between molecules gets larger.

As with the noble gases, the halogens do have similar properties but not exactly the same ones. For example, the reactivity of the element decreases as you descend the group.

This can be seen if we observe the reaction between iron wool and the different halogens.

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So why are the halogens reactive?

The answer lies in the electronic configurations and specifically their outer shell electron configurations. The halogens need only gain 1 electron from another atom to gain more stability.

Fluorine is the most reactive since the electron it is attempting to attract is coming into a shell closest to the positive nucleus. Greater attraction means that it is easier to gain an extra electron - therefore it is the most reactive.

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