Question

1)Lithium is the strongest reducing agent among all the akali metal inspite of high ionisation energy Give reason

2)Lithium forms only monoxide

Answer 1

Part a)
Li is the strongest reducing agent this is due to low electrode potential(-3.05 V)
the more negative the electrode potential, higher is the tendency of the element to lose electrons and hence stronger is the reducing agent.
Electrode potential depends upon:

1. Heat of sublimation: Li(s) ---> Li(g)
2. Ionisation energy: Li(g) --> Li+(g) + e-
3. Hydration energy: Li(g) + aq ---> Li+(aq) + heat of hydration

Now since Li+ ions is smallest in size, therefore large amount of energy is released as heat of hydration which compensates for the high amount energy required as ionisation energy, thereby facilitating the release of electron. Hence Li has low elctrode potential ( -3.05 V) and that is why it is strongest reducing agent.

Part b)
The atomic size of lithium is very small and has a strong positive field around it, therefore it can form bond with one oxygen atom. As the size of atom increases, its holding capacity also increases.
On combination with oxide anion, the positive field of lithium ion restricts the spread of negative charge towards another oxygen atom and thus prevents the formation of a higher oxide.