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Electronic configuration of . The number of unpaired electron in  is 1 after losing 3 electron, Ti has 1 electron left d-orbital     T
Electronic configuration of . The number of unpaired electron in  is 2 after losing 3 electron, V has 2 electron left d-orbital    
Electronic configuration of chromium is . The number of unpaired electron in  is 3 after losing 3 electron, Cr has 3 electron left d-orbital  
The number of unpaired electron in  is 4 after losing 3 electron, Mn has 4 electron left.
In the first transition series, Cu (copper) exhibits +1 oxidation states most frequently. This is because has stable electronic configuration of  . the fully filled d-orbital makes it highly stable.
In a chemical reaction a substances gets oxidised as well as reduced simultaneously is called disproportionation reaction. For examples-
The  configuration is very unstable in ions because after losing one more electron it attains stable configuration.
Cobalt (II) is more stable in aq. solution but in presence of strong field ligand complexing agents, it gets oxidised to  Cobalt (III). Though the third ionisation energy of  is high but the CFSE (crystal field stabilisation energy) is very high in presence of strong field ligand which overcomes the ionisation energy.
is strongly reducing in nature. It has  configuration. By losing one electron it gets oxidised to (electronic configuration ) which can be written as  and it is a more stable configuration. On the other hand  has also  configuration by accepting one electron it gets reduced and act as strongly oxidising agent(electronic configuration ). Thus it is extra stable due to half -filled with d-orbital. 
In lanthanoid series, an earlier member of the series is more reactive, and that is comparable to . with an increase in atomic number, lanthanoids starts behaving similar to aluminium. Actinoids are highly reactive metals, especially when they are finally divided. When we add them into the water, they give a mixture of oxide and hydride. Actinoids combine with most of the non-metals at...
The principle oxidation state of lanthanoids are +3, but sometimes it also shows +2 and +4 oxidation states. This is due to the extra stability of fully- filled and half filled orbitals. Actinoids have a greater range of oxidation states due to comparable energies of and it also has principle oxidation state is +3 but have more compounds in +3 oxidation states than lanthanoids.
Similar to lanthanoids, actinoids also shows actinoid contraction. But the contraction is greater in actinoids because of poor shielding effects of 5f orbitals
The general electronic configuration of actinoids series is  and that for lanthanoids are . 5 orbitals do not deeply participate in bonding to a large extent.
According to our observation, except scandium, all other elements of the first row shows +2 oxidation state. On moving from  to  the number of oxidation states increases but from to number of oxidation states decreases due to a decrease in unpaired electrons. The stability of +2 oxidation state increase on moving from  to  due to increase in difficulty level of removal of the third electron...
Ions which have incomplete d-orbital, they are able to do  transition, which is responsible for colour. And those which has vacant d-orbitals or complete -orbitals are colourless Purple green colourless pink     yellow blue pink   colourless From the table, we notice that and have and configuration, so their aqueous solutions are colourless. All others are coloured in...
The  value of  is higher than that of  but less than that of . So, the reduction of ferric ion () to ferrous ion() is easier than  but as not easy as . Hence ferric ion is more stable than manganese ion(), but less stable than chromium ion(). Order of relative stablities of different ions is-  
When acidified permanganate solution react with oxalic acid () it converts oxalic acid into carbon dioxide () Here are the reacions- --------------------------------------------------------------------------------------------------      overall reaction 
Reaction of acidified permanganate solution with sulphur dioxide (). It oxidises the  to sulphuric acid () Here are the reactions- ------------------------------------------------------------------------------------------------  
Potassium permanganate can be prepared from the fusion of pyrolusite ore() with an alkali metal hydroxide and an oxidising agent (like ). This gives dark green . It disproportionates in acidic or neutral medium to give permanganate. (i)Acidified permanganate ion reacts with iron- -------------------------------------------------------------------------------
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