AP EAMCET · Chemistry · Classification of Elements and Periodicity in Properties

\(Assertion\) (A) Helium and beryllium have similar outer electronic configuration \(n s^2\).
\(Reason\) (R) Both are chemically inert

A Both \((A)\) and \((R)\) are correct and \((R)\) is the correct explanation of \((A)\).
B Both \(\mathrm{A}\) and \(\mathrm{R}\) are correct but \(\mathrm{R}\) is not the correct explanation of \(\mathrm{A}\).
C \(A\) is correct but \(R\) is incorrect.
D Both \(A\) and \(R\) are incorrect.

Verified Solution

Answer & Solution

Correct Answer

(C) \(A\) is correct but \(R\) is incorrect.

Step-by-step Solution

Detailed explanation

The electronic configuration of \(\begin{aligned} \mathrm{He} & =1 s^2 \\ \mathrm{Be} & =1 s^2 2 s^2\end{aligned}\) Both have \(n s^2\) configuration but helium is inert because its only shell i.e. \(1 s\) is completely filled while Be is a reactive alkaline earth metal. So, A…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From AP EAMCET

Explore more questions on app

\(Assertion\) (A) Helium and beryllium have similar outer electronic configuration \(n s^2\).\(Reason\) (R) Both are chemically inert

Step-by-step Solution

\(Assertion\) (A) Helium and beryllium have similar outer electronic configuration \(n s^2\).
\(Reason\) (R) Both are chemically inert