Question

Match List-I with List-II
{|p{7cm}|p{7cm}|} List-I (Element) & List-II (Electronic Configuration)
(A) Mg & (I) 2, 1
(B) Na & (II) 2, 8, 7
(C) Li & (III) 2, 8, 1
(D) Cl & (IV) 2, 8, 2

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (I), (B) - (III), (C) - (IV), (D) - (II)
• (A) - (IV), (B) - (III), (C) - (I), (D) - (II)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

To solve atomic structure matching questions quickly, use the group number of the periodic table:
- Lithium (Group 1, Period 2) has 1 valence electron: 2, 1.
- Sodium (Group 1, Period 3) has 1 valence electron: 2, 8, 1.
- Magnesium (Group 2, Period 3) has 2 valence electrons: 2, 8, 2.
- Chlorine (Group 17, Period 3) has 7 valence electrons: 2, 8, 7.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The electronic configuration of an atom describes how its electrons are distributed among different energy levels (shells).
The maximum number of electrons that can be accommodated in the $n$-th shell is given by the formula $2n^2$, where $n = 1$ is the K shell, $n = 2$ is the L shell, and $n = 3$ is the M shell.

Step 3: Detailed Explanation:
Let us determine the electronic configurations of each element based on their atomic numbers ($Z$):
(A) Magnesium (Mg):
The atomic number of Magnesium is 12, meaning a neutral atom has 12 electrons.
The K shell ($n=1$) holds 2 electrons, the L shell ($n=2$) holds 8 electrons, and the remaining 2 electrons go to the M shell ($n=3$).
Thus, its configuration is 2, 8, 2.
Hence, (A) matches with (IV).
(B) Sodium (Na):
The atomic number of Sodium is 11, meaning a neutral atom has 11 electrons.
The K shell holds 2 electrons, the L shell holds 8 electrons, and the remaining 1 electron goes to the M shell.
Thus, its configuration is 2, 8, 1.
Hence, (B) matches with (III).
(C) Lithium (Li):
The atomic number of Lithium is 3, meaning a neutral atom has 3 electrons.
The K shell holds 2 electrons, and the remaining 1 electron goes to the L shell.
Thus, its configuration is 2, 1.
Hence, (C) matches with (I).
(D) Chlorine (Cl):
The atomic number of Chlorine is 17, meaning a neutral atom has 17 electrons.
The K shell holds 2 electrons, the L shell holds 8 electrons, and the remaining 7 electrons go to the M shell.
Thus, its configuration is 2, 8, 7.
Hence, (D) matches with (II).

Step 4: Final Answer:
The correct matching sequence is:
(A) - (IV), (B) - (III), (C) - (I), (D) - (II).
This corresponds to Option (C).