The Periodic Table
The chemistry of an element is governed by the outer electrons in which it has. We arrange elements in groups according to their outer structure. Ionisation energy and electronegatvity increase diagonally across the table (across a period and up a group)
Valency normally rises with group number up to a maximum of four and then falls to one in group 7. Elements are generally metals when IEs are low in the left and lower regions of the table and the d black transition elements; non-metals occur in the high I.E, upper right, portion and semiconductor elelemtns, such as silicion, are found between these two regions.
Melting temperatures trends are more complex, depending on atomic mass, bond type and the type of solid structure but decrease down Group 1, rise down Group 7, increase across a period up to Group 4 (carbon melts above 3500) and the drop sharply as elements form diatomic molecules held in the solid by weak intermolecular forces.
Many chemical reactions involve losing or gaining electrons. A species is being oxidised if it loses electrons and it's being reduced it if gains electrons. Since electrons don't vanish or appear from nowhere, all these reactions involve a transfer of electrons from the species being oxidised to the one being reduced. You can remember this by the nemonic OILRIG.
O - Oxidation
I - Is
L - Loss
R - Reduction
I - Is
G - Gain
Oxidation Numbers (states)
This is a useful system for redox with these simple rules:
1. All elements have an oxidation state of zero
2. Hydrogen in compounds is usually 1, or maybe +1
3.Oxygen is usually -2 or -11
4. Group 1 and 2 elements in compounds are 1 and 2 respectively
5. Group 6 and 7 elements in compounds are usually -2 and -1 respectively
6. An element bonded to itself is still 0
7. The oxidation numbers of the elements in a compound or ion must add up to zero or the charge of the ion
The S-block elements
These elements are all reactive, electropositive (low electronegativity) metals forming cations with the oxidation numbers 1 or 2 respectively.
Oxides are formed…