Hydrogen
Hydrogen has 1 electron in its outer energy level and is in Group 1. It can for H+ metals although this can only exist in a solution, however the element Hydrogen consists of diatomic molecules.
The Noble Gases
They are at the far end of the Periodic Table.
These are elements of Group 0.
They are all un-reactive.
They exist as individual atoms rather than diatomic.
Used as Inert Gases as in filament lamps (E.g. Argon).
The Transitional Metals
They are in the middle of the Periodic Table.
These are very hard with high M.P.
They are used as catalysts.
They form coloured compounds.
At the boundary of the periodic table, there is a line separating metals and non-metals. These elements are known as semi-metals. They include Boron, Arsenic and Silicon.
Silicon is Hard, Shiny and has a high M.P. It is a semi-conductor and it conducts 10,000,000 times better than a non-metal, but 1,000,000,000 times worse than a metal.
Some Special Structures
Fibres
These are formed by forcing molten plastics through tiny holes. These fires generally stretch and solidify. This process aligns the molecules along the length of the fibre.
Glass
This is an irregular giant structure of silicon and oxygen atoms held together by strong covalent bonds. Tiny surface cracks make glass brittle and weak in tension.
Pottery
This is the heating of clay to high temperatures and it is a ceramic materiel (A Mass of tiny crystals bonded together by glass).
Plastics (Polymers)
A Polymer is a long chain molecule with a repeating unit. e.g. Poly(Chlorothene)
CnH2n
n = a number greater than 1000 but less than 10000
Plastics are tangled mass of these long molecules. The covalent bonds are strong.
In thermo-softening plastics, the forces between the chains are weak so the plastic softens when heated.
In thermosetting plastics, when the plastic is first heated, covalent bonds are formed between the chains. These strong cross linkages prevent them from being re-moulded. e.g. Bakelite in cooker control knobs.