Question

The nitrogen atoms in \(\mathrm{N}_{2}\) participate in multiple bonding, whereas those in hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4}\), do not. (a) Draw Lewis structures for both molecules. (b) What is the hybridization of the nitrogen atoms in each molecule? (c) Which molecule has a stronger \(\mathrm{N}-\mathrm{N}\) bond?

Short answer

The Lewis structures are N≡N for N2 and H2N-NH2 for N2H4. The nitrogen atoms in N2 are sp hybridized, while those in N2H4 are sp3 hybridized. The N-N bond in N2 (triple bond) is stronger than the N-N bond in N2H4 (single bond).

Step-by-step solution

Draw Lewis Structures

To draw the Lewis structures for N2 and N2H4, start by counting the total number of valence electrons in each molecule. Nitrogen has 5 valence electrons, and hydrogen has 1. N2: 2 nitrogen atoms * 5 electrons each = 10 valence electrons N2H4: 2 nitrogen atoms * 5 electrons each + 4 hydrogen atoms * 1 electron each = 14 valence electrons Now, draw the Lewis structures. For N2: 1. Place two nitrogen atoms together, with one single bond. 2. Add 3 more pairs of electrons to each nitrogen atom to complete the octet. 3. To minimize formal charge, turn one lone pair into a bonding pair, resulting in a triple bond. Lewis Structure for N2: N≡N For N2H4: 1. Place two nitrogen atoms together with a single bond. 2. Add 2 hydrogen atoms to each nitrogen atom, with single bonds. 3. Add 2 remaining electrons (1 lone pair) to each nitrogen atom. Lewis Structure for N2H4: H2N-NH2

Determine Hybridization

To find the hybridization, count the electron groups around each nitrogen atom. Electron groups include single bonds, double bonds, triple bonds, and lone pairs. For N2: Each nitrogen atom has 1 triple bond and 1 lone pair, which corresponds to 2 electron groups. This suggests sp hybridization. For N2H4 (hydrazine): Each nitrogen atom has 2 single bonds to hydrogen atoms, 1 single bond to another nitrogen atom, and 1 lone pair, which corresponds to 4 electron groups. This suggests sp3 hybridization. Nitrogen in N2: sp hybridization Nitrogen in N2H4: sp3 hybridization

Compare N-N Bond Strength

The N-N bond strength generally increases in the order single bond < double bond < triple bond. As a result, the N-N bond in N2 (triple bond) is stronger than the N-N bond in N2H4 (single bond). The molecule with a stronger N-N bond is N2.