Friday, 28 January 2011


The Halogens are 5 non metallic group 7 elements in the periodic table. They have slightly different properties because of their electronic setting (having 7 electrons in their outermost shells).

The most significant property of Halogens is their greatly high reactivity.

In terms of patterns and trends, as you move further down the group, electronegativity and reactivity decreases, while boiling points increase. (Exception of Astatine, because that stuff's radioactive).

Halogens have a high electronegativity, and are particularly reactive to form stable ionic crystals (Salts) as the name suggests, halo meaning salt and gen meaning to form.

**Sodium Chloride is the most abundant Halogen-produced Salt**

Sodium Chloride Crystals

The charge density of the nucleus of Halogens is important because it shows that they have a high proton charge, which grants them a good electronegativity making them ideal anions, for pairing with the 1st group cations such as Na+.

Halogens, as they have 7 electrons in their outer shells, have an oxidation number of -1, with a few exceptions, for example if it was binded with Oxygen or another Halogen that is more reactive, with Fluorine being the most reactive one.

The difference in reactivity between the group 7 elements is within the fact that they're in consecutive periods, meaning there's a hierarchy relating between the number of outermost shells and the reactivity of the element. This is relating to the idea that more rings around the nucleus make the outer-most shell further away from the centre point of electronegativity, so the pull is spread over a large area decreasing its concentration.

Halogens as oxidation agents follow this general form:

Sunday, 23 January 2011

Electrophilic Addition

Electrophilic addition is basically this:
Like when you have a retarded bond that decides to jam itself into an unsaturated alkene. A bit like that relative you never liked. 

This happens in some stupid stages you're meant to remember. As if it'll mean anything to you in life.

Stage number one. The retarded bond ATTACKS the chilling alkene.

As the chilling alkene gets shanked by the retarded bond, one of its bonds snaps off. The electron's left hanging there.
As the bond's snapped off, the retarded bond makes advantage of this via exploiting the open port, as the following diagram illustrates.
And then we get this:

And then,
So, we end up with this: