Electronic Configuration — Prelims Strategy

Prelims Strategy

For NEET Prelims, a systematic approach to electronic configuration questions is vital. \n1. Memorize the Aufbau Order: Practice the $1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p$ sequence.

The diagonal rule (Moeller diagram) is an excellent visual aid. \n2. Master Exceptions: Chromium ($[Ar] 3d^5 4s^1$) and Copper ($[Ar] 3d^{10} 4s^1$) are mandatory. Be aware of other less common exceptions like Molybdenum ($[Kr] 4d^5 5s^1$) and Silver ($[Kr] 4d^{10} 5s^1$).

\n3. Ions - The 'n' Rule: For cations, always remove electrons from the orbital with the highest principal quantum number (n) first. For transition metals, this means removing 4s electrons before 3d electrons (e.

g., $Fe^{2+}$ is $[Ar] 3d^6$, not $[Ar] 3d^4 4s^2$). For anions, add electrons to the lowest available energy orbital. \n4. Hund's Rule for Unpaired Electrons: When determining paramagnetism/diamagnetism, draw orbital diagrams for the valence shell to correctly apply Hund's rule and count unpaired electrons.

\n5. Quantum Numbers: Understand the rules for each quantum number's possible values ($l \le n-1$, $-l \le m_l \le +l$). Practice identifying valid and invalid sets. \n6. Practice: Solve a wide variety of MCQs, especially those involving transition metal ions and magnetic properties, as these are common trap questions.

Time management is key, so quick and accurate application of rules is essential.