The electronic configuration of metal ‘A’ is 2,8,1 and that of metal ‘B’ is 2,8,2.

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The electronic configuration of metal ‘A’ is 2,8,1 and that of metal ‘B’ is 2,8,2. Which of the two metals is more reactive? Write their reaction with dilute hydrochloric acid.

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• 1)  moving from left to right in a period of periodic table, the chemical reactivity of elements first decreases from sodium to silicon and then increases from phosphorus to chlorine.
• The electronic configuration of metal ‘A’ is 2,8,1. This is electronic configuration of sodium metal.
• The electronic configuration of metal ‘B’ is 2,8,2. This is electronic configuration of magnesium metal.
•  In the first element of third period, sodium, there is 1 valence electron which it can lose easily to react with other substances, so it is very reactive metal.
• The second element magnesium has 2 valence electrons. It is not easy for an atom to lose 2 electrons, so magnesium is less reactive than sodium.

Reaction with dil hydrochloric acid:
Na + HCl → NaCl + H2Mg + HCl → MgCl2 + H2