The Transition Elements: Variable oxidation states. The common oxidation states

All transition metals except Sc are capable of having various oxidation states. The 4s electron are first used and then the 3d electrons.

This happens because the 4s and 3d electrons have similar energy.

The known oxidation states can be summarized by this table:





http://www.s-cool.co.uk/a-level/chemistry/transition-metals/revise-it/variable-oxidation-states

The Transition Elements: General physical & chemical properties and periodicity

• high melting point and boiling points
• conduct electricity and heat
• malleable and ductile
• low ionization energies
• wide range of oxidation states, but are all positive
• positive oxidation states allow for ionic and partially ionic compounds
• five d orbitals become more filled from left to right on periodic table

http://chemistry.about.com/od/elementgroups/a/transitionmetal.htm

The Transition Elements: Definition of transition element

A transition metal is an element which forms one or more stable ions which have incompletely filled d orbitals.

http://www.chemguide.co.uk/inorganic/transition/features.html

The Transition Elements: Electron configurations. Ionization energies and relative stability of ions

The main characteristic of the electron configuration of transition elements is that they have full outer sub-orbitals and the second outermost d sub-orbitals incompletely filled.
An exception to this is copper which loses one 4s orbital electron to the 3d suborbital in order to increase stability.

The ionization energies of transition elements remain fairly low even when the atomic number increases.

Transition metal ions have their electrons removed not from the higher energy orbitals, but from the valence shell orbitals.
Transition metals form one or more stable ions with a completely filled d orbital.

http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Electronic_Configurations/Electron_Configuration_of_Transition_Metals_and_Ions%3A_Mn_vs._Cu
http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Ionization-of-Transition-and-Inner-Transition-Elements-904.html
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch12/trans.php

The Transition Elements: The first row d block (Sc to Zn.)

These transition metals have variable oxidation numbers, have high melting points, and are harder and denser than group 1 and 2 metals.
There is no significant change in atomic radii due to the repulsion between the 4s and 3d electrons.
However, Sc and Zn are not considered transition elements because they do not have a partially filled d subshell. They only have one possible oxidation state.

http://www.scribd.com/doc/56633626/13-2-First-Row-D-Block-Elements

Halogens: Hydrogen halides. Acidity and thermal stability

If you use the Bronsted-Lowry definition of an acid as a proton donor, hydrochloric, hydrobromic and hydroiodic acids are all acids. Hydrogen chloride, hydrogen bromide and hydrogen iodide dissolve in and react with water to give their respective acids, which are strong acids.
However, although hydrogen fluoride dissolves in water, hydrofluoric acid is a weak acid.

Hydrogen halides are colorless gases at room temperature. Hydrogen fluoride has a higher boiling point than the other halides because it can form hydrogen bonds. The other hydrogen halides increase boiling points as you go down the periodic table.

http://www.chemguide.co.uk/inorganic/group7/acidityhx.html

Halogens: Metal halides. Reaction with conc. sulphuric acid. Precipitation reactions with silver and lead ions. Tests for halide ions

Concentrated sulfuric acid, when reacted with metal halides, can act as either an acid or an oxidizing agent.
If it is acting as an acid, the concentrated sulphuric acid gives a hydrogen ion to the halide ion to produce a hydrogen halide.
e.g. NaCl + H2SO4 --> HCl + NaHSO4
If it is acting as an oxidizing agent, how it reacts with halides depends on the halide itself.
Concentrated sulfuric acid is not a strong enough oxidizing agent to oxidize fluoride or chlorine ions.
Bromide ions are strong enough to reduce concentrated sulfuric acid. It will reduce sulfuric acid to sulfur dioxide gas and it will be oxidized to bromine.
Iodide ions are stronger reducing agents than bromide ions, so they will reduce sulfuric acid to sulfur dioxide, then to sulfur, then to hydrogen sulfide. 

You can test for halide ions by using silver nitrate. If silver nitrate solution is added to water containing halide ions the silver halide is precipitated. This is because silver halides are insoluble in water.
The same occurs for lead nitrate; the lead halide is precipitated.




http://www.chemguide.co.uk/inorganic/group7/halideions.html
http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/ionic_compounds/ionicanalysisrev5.shtml
http://www.nuffieldfoundation.org/practical-chemistry/silver-and-lead-halides