Question

The reactivity of the metals $Al$ , $Ca$ , $Mg$ and $Na$ follows the order.
(A) $Na\, > Ca\, > \,Mg\, > \,Al$
(B) $Na\, > \,Mg\, > \,Ca\, > \,Al$
(C) $Al\, > \,Mg\, > \,Ca\, > \,Na$
(D) $Mg\, > \,Na\, > \,Ca\, > \,Al$

Answer 1

In the given question the reactivity order of given metal atoms will be decided by their ability to form cations. The reactivity of a metal atom depends upon its tendency on how quickly it loses its electrons present in the valence shell to become a cation.

Complete Step-by-step Answer:
In order to pull the electron from the valence shell of the atom, we have to provide some energy. This energy is called Ionization energy.
It is the measure of how much energy is required for an atom to remove its outermost electron from its valence shell in its gaseous state. So ionization energy becomes a parameter to compare the reactivity of metal atoms. In the periodic table, elements are arranged in Periods (horizontal) and groups (vertical). There are $7$ periods and $18$ groups in the periodic table.
Sodium, magnesium, and aluminum are present in the third period in that order, and magnesium and calcium are present in group second in that order.
In the $3rd$ period, as we shift from left to the right, the ionization energy of elements increases, this shows the decline in the reactivity of those elements so by this we can conclude that sodium is the most reactive metal and after that magnesium and then aluminum in the $3rd$ period.
In the $2nd$ Group, as we shift from top to bottom, the ionization energy decreases, this shows the increase in the reactivity of elements down the order so by this we can conclude that Calcium is more reactive than magnesium.
So by comparing both the positions we can conclude the overall reactivity order of the given four metals as $Na\, > Ca\, > \,Mg\, > \,Al$ .
Hence the right answer is option (A).

Note:
Metals are those elements that lose their electrons and form positive ions (cations) and possess metallic bonds. Metals tend to be lustrous, ductile, malleable, and a good conductor of electricity.