Question

Choose the correct sequence of the elements arranged in their increasing order of atomic numbers:
A. Pu
B. Po
C. Pm
D. Pt
E. Pa
Choose the correct answer from the options given below :

• A. C, D, B, E, A
• B. D, C, A, B, E
• C. A, D, B, C, E
• D. B, E, D, A, C

Hint:

While memorizing the entire periodic table isn't always necessary, you should be broadly familiar with the "blocks". Lanthanides span Z=57 to 71. Actinides span Z=89 to 103. The 5d transition metals span Z=72 to 80. This general knowledge allows you to quickly sort elements even if you forget the exact atomic number.

Answer 1

The Correct Option is A

Step 1: Concept:
The task is straightforward: identify the atomic number ($Z$) for five given chemical elements and arrange them in ascending order.

Step 2: Identifying the Elements and Atomic Numbers:
Let's define each element from its chemical symbol:
- A. Pu: Plutonium. An actinide element, famous for use in nuclear reactors and weapons. Atomic number $Z = 94$.
- B. Po: Polonium. A p-block chalcogen, radioactive, discovered by Marie Curie. Atomic number $Z = 84$.
- C. Pm: Promethium. A lanthanide element, rare and radioactive. Atomic number $Z = 61$.
- D. Pt: Platinum. A heavy transition metal in the 5d series. Atomic number $Z = 78$.
- E. Pa: Protactinium. An actinide element occurring before Uranium. Atomic number $Z = 91$.

Step 3: Step-by-step Explanation:

• Now we arrange the numbers in increasing (ascending) order:
$61 < 78 < 84 < 91 < 94$
• Correlating these values back to the given symbols:
- 61 corresponds to C (Promethium)
- 78 corresponds to D (Platinum)
- 84 corresponds to B (Polonium)
- 91 corresponds to E (Protactinium)
- 94 corresponds to A (Plutonium)

• The final ordered sequence is C, D, B, E, A.

Step 4: Final Answer:
The correct arrangement based on atomic numbers is found in option (A).