Due to its small size, removal of valence electrons of boron requires very high energy. Therefore, boron does not form +3 ions, but it forms covalent compounds. Boron is less electronegative than even hydrogen. So, compounds of boron contain boron in a positive oxidation state, generally +3.

+3

The +1 oxidation state becomes more stable as we go down the group. This is due to inert pair effect. In the case of last element, after the removal of one electron form p-orbital.

Hydrogen has a -1 oxidation state in BH3. Therefore B is +3, each H is -1.

Oxidation number of Si in SiH4. This seems to be a double displacement (metathesis) reaction, where Si has oxidation state −4.

In hydrogen peroxide H2O2, the oxidation number of O is -1 and the range of the Oxidation number that O can have are from O to -2 can sometimes also attain the oxidation numbers +1 and +2. Hence, H2O2 can act as an oxidising as well as reducing agent.

C is using an oxidation state of 1 . This is the full list of oxidation states for this molecule.

-2

+ 6

+5

The oxidation states of middle sulphur atoms are 0 each and terminal sulphur is +5 each.

+2

Potassium trioxalatoiridium (III)

potassium hexacyanoferrate(II)

Iron cyanide

CN is a powerful field ligand and uses inner 3d-orbitals to form a low spin complex. Because there are 6 ligands, it has octahedral geometry. So the hybridization of the complex is d2sp3.

According to valence bond theory in [Fe(CN)6]4 – complex Fe+2 involves d2sp3 hybridization that is inner orbital complex having no unpaired electron and hence it is diamagnetic.

FeCl3