Question

Consider the following radioactive decays

I. $_{92}U \xrightarrow{-\alpha} _{90}Th$ and

II. $_{90}Th \xrightarrow{-\alpha} _{88}Ra$

In which case group of parent and daughter elements remains unchanged.

• A. In (I)
• B. In (II)
• C. Both in (I) and (II)
• D. None of the above

Answer 1

Answer: (A)

In (I)

Answer 2

Let's analyze the two radioactive decays:

I. $_{92}U \xrightarrow{-\alpha} _{90}Th$: Both Uranium (U) and Thorium (Th) are part of the Actinide series. The Actinide series is typically considered part of Group 3. Thus, Group 3 -> Group 3, so the group remains unchanged.

II. $_{90}Th \xrightarrow{-\alpha} _{88}Ra$: Thorium (Th) is part of the Actinide series (Group 3). Radium (Ra) is an Alkaline Earth Metal (Group 2). Thus, Group 3 -> Group 2, so the group changes.

Therefore, the group of parent and daughter elements remains unchanged only in case (I).