Answer the following question:
 
i. Name an element which has two valencies.
 
has two valencies. It can exhibit as
 
ii. Which out of aluminium and aluminium ion is more stable and why?
 
is more stable because the electronic configuration is . It has lost three electrons to achieve the stable electronic configuration of neon. Whereas the electronic configuration of is and needs to lose three electrons to achieve a stable electronic configuration, making it less stable.