Question

Atomic number of metal A is 11 while atomic number of metal B is 20 which of them will be more reactive .write chemical reaction of dilute HCl with metal A

Answer 1

Atomic number of A is 11 so
Electronic configuration of A is 2,8,1

Atomic number of B is 20 so
Electronic configuration of B is 2,8,8,2

Metal A is more reactive because it has only one valence electron to lose and it will lose it readily.

Reaction

A + HCl --> ACl + H

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Answer 2

The metal with atomic number 11 is:

Sodium

Electronic configuration: 2, 8, 1

The metal with atomic number 20 is:

Calcium

Electronic configuration: 2, 8, 8, 2

Reactivity:

The valence shell of sodium is half filled whereas the valance shell of calcium is fully filled. The electrons readily fill the half filled shell. Thus, the reactivity of sodium is more than the reactivity of calcium.

Chemical reaction of dilute HCl with sodium:

2 Na + 2 HCl → 2 NaCl + H₂