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Which of the following is least reactive?
Na
K
Ca
Mg
Mg
Magnesium (Mg) is the least reactive metal among the options provided (Na, K, Ca, Mg) because it lies below the others in the electrochemical series. Reactivity of these group 1 and group 2 metals increases down the group and across the period from right to left; since Mg is in Group 2 and has a higher ionization energy compared to alkali metals and calcium, it is the least reactive in this set.
Magnesium (Mg) is the least reactive metal among the options provided (Na, K, Ca, Mg) because it lies below the others in the electrochemical series. Reactivity of these group 1 and group 2 metals increases down the group and across the period from right to left; since Mg is in Group 2 and has a higher ionization energy compared to alkali metals and calcium, it is the least reactive in this set.
Think of reactivity as how easily a person 'gives away' their belongings; potassium is like someone extremely generous who gives away everything instantly, while magnesium is more cautious and holds onto its electrons a bit more tightly.
Remember the reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au.
IE1тАЛтИЭatomic┬аradius1тАЛ тАФ reactivity is inversely related to the ease of electron removal (Ionization Energy).
The reactivity of metals is determined by their ability to lose electrons to form positive ions (cations). Alkali metals (K, Na) are highly reactive due to their low ionization energies, and among alkaline earth metals, reactivity increases with atomic size because the valence electrons are further from the nucleus and more easily lost. Magnesium has a smaller atomic radius and higher effective nuclear charge than the others in the list, making its electrons more tightly held and harder to lose.
Reactivity of metals increases down a group due to increased atomic size and shielding.
Group 1 metals (Alkali) are always more reactive than Group 2 metals (Alkaline Earth) in the same period.
Potassium (K) is the most reactive metal in this list, followed by Sodium (Na), Calcium (Ca), and finally Magnesium (Mg).
Magnesium is less hazardous to handle in a laboratory setting compared to highly reactive alkali metals like Potassium or Sodium.
Because it is less reactive, Magnesium does not displace hydrogen from water as vigorously as the other three metals listed.
Magnesium is used in lightweight alloys for aerospace components.
Magnesium is used in flares and fireworks due to its bright white light upon combustion.
Potassium and Sodium must be stored under oil to prevent reaction with air/moisture.
Magnesium reacts slowly with cold water but vigorously with steam.
D is correct тАФ Magnesium (Mg) is the least reactive among the given choices because it is an alkaline earth metal with higher ionization energy than the alkali metals (K, Na) and the larger alkaline earth metal (Ca).
Always remember that in the Periodic Table, reactivity for metals increases as you move down a group and to the left across a period.
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