Question

Assertion :Sodium and aluminium have atomic numbers $11$ and $13$, respectively. They are separated by one element in the periodic table, and have valencies $1$ and $3$ respectively. Chlorine and potassium are also separated by element in the periodic table (their atomic number being $17$ and $19$ respectively) and yet both have valency $1$. Reason: Cl requires one electron to complete its octet and its valency is $1$ while $K$ has one electron in its outermost shell which it can easily loose to complete its octet and can attain the most balanced state after forming an octet. So both has valency $1$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Chlorine =$17=2,8,7$ while potassium=$19=2,8,8,1$. So $Cl$ requires one electron to complete its octet and its valency is $1$ while $K$ has one electron in its outermost shell which it can easily loose to complete its octet and can attain the most balanced state after forming an octet. So both has valency $1$.