Group 7 & Group 0 (Halogens & Noble Gases)

 Halogens are very dangerous, these are the Halogens:

Florine is a poisonous yellow gas and is very reactive.

Chlorine is less reactive than fluorine but is a poisonous green gas.

Bromine is a dark brown liquid, once again the odour and liquid are poisonous, and the vapour that it creates is heavy, so you can pour out its vapour from a glass ampule

Iodine is a dark purple solid that forms poisonous purple vapours, but it is also a commonly used antiseptic in medical applications. 

Tennessine.

Atatine.

But we will mainly talk about the elements starting from Florine to Iodine, but the elements Tennnessine and Atatine are still important to remember.

All halogens exist as pairs of atoms, referred to as diatomic molecules. This term indicates that these molecules consist of two atoms. They form these pairs by sharing electrons through covalent bonds. Additionally, halogens can bond with other non-metals, such as carbon or hydrogen, using the same covalent bonding mechanism.
Chlorine bonding with Carbon can get you Carbon Tetrachloride.

Unlike the Alkali metals, the Halogens increase their boiling and melting points the further down you go on the chart.
Along with the boiling points increasing, the reactivity decreases, making the elements less reactive.

The reason why they become less reactive is because the electrons get further from the positive nucleus.

When Halogen ionic bonds with metals and collects an electron to become a minus -1 electron, we call those Halides, so we change the 'ne' at the ends of the names of the Halogens so when Bromine bonds with a metal it becomes Bromide, Iodine becomes Iodide, Chlorine becomes Chloride, and Fluorine becomes Fluoride.

Most of the time they bond with the Alkali metals, an example is Sodium Chloride, the Sodium is an alkali metal while the Chloride is a Halogen.

Another thing that Halogens do is that they do something called 'Displacement Reactions', which means that the more reactive Halogen displace the less reactive ones.

So if we pumped some Chlorine gas into a solution of Potsassium Bromide, so the chemical numbers would be Cl(g) + 2kBr(aq), so since the Chlorine is more reactive than the Bromine it will displace the Bromine causing the element to become 2kCl(aq).

Something to keep in mind is that more reactive Halogens will always displace less reactive ones.