[siewwen168]

how to identify which is good oxidizing agent ,good reducing agent or neither?
F-, KIO3, NO3-, K, Fe2+, F2, Na+, NH3
 
is it any specific method to identify???

[xiankai]

a good oxidising agent is easily oxidised, which means the reaction must be favourable, that'll be require a more stable product than the reactant. vice versa for a good reducing agent.

for example, F- can only be oxidised to F₂. which form of the element is more stable? F- , because F2 is too reactive and will readily combine with other elements to form a product. if it is not a good reducing agent, can it be a good oxidising agent? only if it can be further reduced into a more stable compound. this is clearly not the case, so F- is neither.

try applying common definitions of each of the ions to see if which form is more stable. also, thinking about their ease of electron discharge (electronegativity or electron affinity), ease of electron acceptance (ionisation energy) will help u determine the levels of stability between different charges.

[jdurg]

Remember, an oxidizing agent is something that will oxidize something else, and in the process be reduced.  (So xiankai was a bit off there).  When something is oxidized, it loses electrons and becomes more positive.  When something is reduced, it gains electrons and becomes more negative.  So an oxidizing agent will gain electrons from what it's reacting with and a reducing agent will lose electrons to whatever it's reacting with.

So to be a good reducing agent, the species must be able to readily give up electrons and become more positive.  

A good oxidzing agent must be able to readily take electrons and become more negative.

A substance falls into the 'neither' category if it won't readily take on or give up any electrons.