Which is most reactive elements among Na, mg and al?​

Explanation:

As we move from left to right in a period the chemical reactivity of a metal decreases and of non-metal increases. Hence Na is most reactive as it is the first element of period 3.

sodium(Na)

Explanation:

A reactive metal has the ability to easily lose an electron and acquire a positive charge. Sodium easily loses electrons and acquires a positive charge. Sodium easily lose electrons than magnesium and get oxidized to easily.