Question

Assertion Electron capture occurs more than positron emission in a heavy nucleus.
Reason In a heavy nucleus, electrons are relatively close to nucleus.

• A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
• B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
• C. If Assertion is true but Reason is false.
• D. If both Assertion and Reason are false.

Answer 1

Answer: (A)

In a heavy nucleus, the electrons are relatively close to nucleus, which promotes their interaction with the nucleus. Thus, electron capture is more often than positron emission in decay of heavy nucleus. Since nearly all unstable nuclei found in nature are having high $Z$, positron emission was not discovered untill several decades after electron emission had been established.