Tetravalence of Carbon — Prelims Strategy

Prelims Strategy

For NEET Prelims, questions on tetravalence of carbon are typically direct and conceptual, or involve simple calculations like counting bonds. The strategy should focus on: \n\n1. Mastering Hybridization: Be able to quickly identify the hybridization state ($sp^3, sp^2, sp$) of any carbon atom in a given structure.

Remember the rule: count the number of sigma bonds and lone pairs around the carbon. 4 $\sigma$ bonds = $sp^3$; 3 $\sigma$ bonds = $sp^2$; 2 $\sigma$ bonds = $sp$. \n2. Memorizing Geometries and Bond Angles: Directly associate $sp^3$ with tetrahedral ($109.

5^\circ$),$sp^2$with trigonal planar ($120^\circ$), and$sp$with linear ($180^\circ$). These are frequently tested facts. \n3. **Counting Sigma and Pi Bonds:** Practice drawing expanded structures and systematically counting single bonds (1$\sigma$), double bonds (1$\sigma$, 1$\pi$), and triple bonds (1$\sigma$, 2$\pi$).

Pay close attention to C-H bonds and bonds within alkyl groups. \n4. **Understanding $s$-character:** Know that $s$-character increases from $sp^3$ (25%) to $sp^2$ (33.3%) to $sp$ (50%). This directly impacts electronegativity, bond strength, and acidity (e.

g., acidity of terminal alkynes). \n5. Avoid Trap Options: Distractors often involve mixing up bond angles or hybridization states. Carefully read the question and options. For numerical problems, double-check your counting.

For conceptual questions, ensure your reasoning aligns with the fundamental principles of VSEPR and hybridization. Practice with a variety of structures, including cyclic compounds and functional groups.