Question

Draw the Lewis structure for hydroxylamine, \(\mathrm{H}_{2} \mathrm{NOH} .\) What is the hybridization for nitrogen and oxygen in this molecule? What orbitals overlap to form the bond between nitrogen and oxygen?

Short answer

N and O are both sp\(^3\) hybridized. The N-O bond is formed by sp\(^3\)–sp\(^3\) overlap.

Step-by-step solution

Count Total Valence Electrons

Identify the number of valence electrons for each atom. Hydrogen (H) has 1, Nitrogen (N) has 5, and Oxygen (O) has 6. Hydroxylamine (\(\mathrm{H}_2\mathrm{NOH}\)) consists of 2 H, 1 N, and 1 O, leading to a total of \(2(1) + 5 + 6 = 13\) electrons.

Choose a Central Atom

Nitrogen, being less electronegative than oxygen, is selected as the central atom. The initial skeletal structure is\(\text{H}-\text{N}-\text{O}-\text{H}\).Distribute the hydrogens around the nitrogen and oxygen.

Distribute Electrons to Form Bonds

Place pairs of electrons between N-H, N-O, and O-H to form single bonds. This uses \(4 \times 2 = 8\) electrons, leaving 5 electrons.

Distribute Remaining Electrons to Fulfill Octets

Distribute the remaining 5 electrons. Add a lone pair to nitrogen and two lone pairs to oxygen. This gives nitrogen 8 electrons (counting bonds and lone pair) and oxygen 8 electrons, fulfilling the octet rule.

Determine Hybridization of Nitrogen

In this structure, nitrogen forms 3 sigma bonds and holds one lone pair. This implies sp\(^3\) hybridization for nitrogen.

Determine Hybridization of Oxygen

Oxygen forms 2 sigma bonds and holds two lone pairs. This implies sp\(^3\) hybridization for oxygen.

Orbitals Overlapping for the N-O Bond

For the nitrogen-oxygen single sigma bond, the overlapping occurs between the sp\(^3\)-hybridized orbitals of nitrogen and oxygen.

Key concepts

Valence Electrons

Valence electrons are crucial in determining how atoms bond and form molecules. These are the electrons located in the outermost shell of an atom and are responsible for chemical interactions. Understanding how many valence electrons an atom has helps in predicting its bonding behavior.

For example, in hydroxylamine, \(\mathrm{H}_2\mathrm{NOH}\), hydrogen has 1 valence electron, nitrogen possesses 5, and oxygen has 6 valence electrons. To determine the total number of valence electrons in hydroxylamine, you simply sum these values for all atoms involved:

• Hydrogen: 2 atoms \( \times 1 = 2 \) electrons
• Nitrogen: 1 atom \( \times 5 = 5 \) electrons
• Oxygen: 1 atom \( \times 6 = 6 \) electrons

This results in a total of 13 valence electrons. This count is fundamental in accurately drawing the Lewis structure and ensuring that the electrons are arranged correctly to satisfy each atom's bonding requirements.

Hybridization

Hybridization refers to the mixing of atomic orbitals to form new, hybrid orbitals which are more suitable for the pairing of electrons to form chemical bonds in molecules. It helps explain the geometry of molecular structures.

In hydroxylamine, nitrogen and oxygen undergo hybridization to form the molecule's structure:

• Nitrogen: With 3 sigma bonds and 1 lone pair, nitrogen is sp\(^3\)-hybridized. This hybridization involves the mixing of one s and three p orbitals, resulting in four equivalent sp\(^3\) hybrid orbitals. These orbitals form the molecular geometry necessary for nitrogen to bond with two hydrogens and one oxygen.
• Oxygen: Similarly, oxygen with 2 sigma bonds and 2 lone pairs also undergoes sp\(^3\) hybridization. This configuration accommodates its bonding with nitrogen and one hydrogen, while the lone pairs reside in the remaining hybrid orbitals.

This understanding of hybridization helps explain not just the formation of the molecule, but also its shape and angle of bonds.

Octet Rule

The octet rule is a chemical rule of thumb that reflects the tendency of atoms to prefer having eight electrons in their valence shell. Achieving this stable electron configuration makes the atom akin to a noble gas, which is chemically inert. Most atoms are more stable when they achieve this octet configuration through bonding.

In hydroxylamine, every atom attempts to satisfy the octet rule:

• Nitrogen: Forms three sigma bonds and possesses one lone pair, reaching a total of eight electrons around it. This satisfies the octet rule and ensures nitrogen's stability in the molecule.
• Oxygen: Forms two sigma bonds and holds two lone pairs, resulting in eight electrons around it. Again, this configuration fulfills the octet rule.

Though hydrogen only requires two electrons (a duet), forming bonds with nitrogen and oxygen helps these nonmetals achieve their octet.

Sigma Bonds

Sigma bonds (\(\sigma\)-bonds) are the strongest type of covalent chemical bond. They are formed by the head-on overlap of atomic orbitals and allow free rotation of the bonded atoms. They play a critical role in the structure and stability of molecules.

In the Lewis structure of hydroxylamine:

• The sigma bonds occur between the hydrogen atoms and nitrogen (\(\text{H-N}\), \(\sigma\) bonds), the nitrogen and oxygen (\(\text{N-O}\), \(\sigma\) bond), and the oxygen and hydrogen (\(\text{O-H}\), \(\sigma\) bond).

In each case, these bonds form from the overlap of sp\(^3\)-hybridized orbitals.Understanding sigma bonds is essential, as they not only constitute the framework of the molecule but also influence its physical and chemical properties. Each sigma bond is crucial in maintaining the molecule's integrity and reactivity.