If you mean what group of elements react the most, the answer is the alkali metals and the halogens because they both only either need to gain or lose one electron. If you mean the most reactive element, it would be fluorine because it has the most electronegativity.
ionic bond is formed between ca and cl forming molecule cacl2 ca has 2 velancy and cl has one velancy (ca has 2 electrons in its outer most shell while cl has 1 electron vecancy in its outermost shell). So ca would make bond with 2 cl atoms
The largest advantage of sodium-ion batteries is the high natural abundance of sodium. This could make commercial production of sodium-ion batteries less expensive than lithium-ion batteries. As of 2020, sodium ion batteries have very little share of the battery market.
