s-block element or compound used for a stated purpose

This type of question, asked 4 times: 2 May 2023 S1, 12 May 2024 S2, 12 May 2026 S2, 13 May 2026 S2. All 4 questions below, oldest first.

Try each one first, then open its answer.

Question 1
2 May 2023 S1
51 $Which element from following is used in photoelectric cells?$
Tap an option to check your answer.
Question 2
12 May 2024 S2
85 $Which element from following is used for cancer treatment?$
Tap an option to check your answer.
Question 3
12 May 2026 S2
13 $Which of the following elements is used as a moderator in nuclear reactors ?$
Tap an option to check your answer.
Question 4
13 May 2026 S2
15 $Which compound is used in medicine as barium meal for intestinal x-ray?$
Tap an option to check your answer.

Question 1