Question

Draw a Lewis structure for hydroxylamine, \(\mathrm{NH}_{2} \mathrm{OH}\).

Short answer

Draw \(\mathrm{N}\) center, \(\mathrm{O}\) bonded to \(\mathrm{N}\) and \(\mathrm{H}\); remaining \(\mathrm{H}\)s bonded to \(\mathrm{N}\), distribute remaining e- as lone pairs on \(\mathrm{O}\).

Step-by-step solution

Understanding the Components

Hydroxylamine \(\mathrm{NH}_{2}\mathrm{OH}\) consists of nitrogen (\(\mathrm{N}\)) and an hydroxyl group (\(\mathrm{OH}\)). Begin by counting the total number of valence electrons available. Nitrogen has 5 valence electrons, each hydrogen has 1, and oxygen has 6. Thus, total electrons: \(5 + 2 \times 1 + 1 + 6 = 14\).

Arrange the Atoms

Position nitrogen at the center connected by a single bond to an oxygen atom and two hydrogen atoms. Connect the remaining hydrogen atom to the oxygen. This arrangement reflects the molecular structure, with the nitrogen forming a bond with oxygen, and both atoms having hydrogen atoms attached.

Distribute Electrons

Assign valence electrons to form bonds. Place single bonds between \(\mathrm{N}\) and \(\mathrm{O}\), \(\mathrm{N}\) and each \(\mathrm{H}\), and \(\mathrm{O}\) and its \(\mathrm{H}\). Each bond uses 2 electrons, so a total of 10 electrons are used in forming 5 bonds (\(2\) each: \(\mathrm{N-H}, \mathrm{N-H}, \mathrm{N-O}, \mathrm{O-H}\)).

Complete the Octet Rule

Distribute the remaining 4 electrons where they can complete the octet. Place them as lone pairs on \(\mathrm{O}\) since it is more electronegative and can accommodate more electrons. \(\mathrm{N}\) is satisfied with 8 electrons around it, including shared electrons.

Verify the Structure

Check that all atoms achieve a satisfied valence shell. \(\mathrm{N}\) has 8 electrons including bonds, \(\mathrm{O}\) has 8 electrons (2 from its bond with \(\mathrm{N}\) and \(\mathrm{H}\), plus 4 as lone pairs). Each \(\mathrm{H}\) has 2 electrons in shared bonding, achieving their duet.

Key concepts

Understanding Valence Electrons

Valence electrons are the outermost electrons of an atom and play a pivotal role in chemical bonding. They are the electrons involved in forming bonds with other atoms. Counting the valence electrons is the first step in determining how atoms will bond in a molecule.
The number of valence electrons for an element can be found using the periodic table. For example:

• Nitrogen (N) has 5 valence electrons.
• Hydrogen (H) has 1 valence electron.
• Oxygen (O) has 6 valence electrons.

In the context of the molecule hydroxylamine, \(NH_2 OH\), adding up these valence electrons gives us a total that indicates how these atoms will interact and bond to form a stable structure. By understanding each atom's valence electrons, we can predict the number of bonds an atom can form and how it can achieve a full outer electron shell.

The Octet Rule

The octet rule is a chemical guideline that reflects atoms' tendency to form bonds until they are surrounded by eight valence electrons, essentially achieving the same electron configuration as a noble gas. For most elements, achieving this configuration leads to higher stability.
The rule primarily applies to main-group elements and aims to satisfy each atom's valences by sharing, losing, or gaining electrons in chemical reactions. In particular, the non-metals, like oxygen and nitrogen, achieve an octet by forming covalent bonds, where electrons are shared between atoms.
An example of this is hydroxylamine (\(NH_2 OH\)). Here:

• Nitrogen forms three covalent bonds to achieve an octet: two with hydrogens and one with oxygen.
• Oxygen forms two covalent bonds: one with nitrogen and one with hydrogen, and it holds two lone pairs to complete its octet.

It's crucial to note that while hydrogen strives for a duet, most other elements prefer an octet in their valence shell, which is important when drawing Lewis structures.

The Nature of Covalent Bonds

Covalent bonds are strong chemical bonds formed when two atoms share one or more pairs of electrons. These bonds typically occur between non-metal atoms with similar electronegativities, allowing each to fill their valence shell through sharing.
In a Lewis structure, covalent bonds are represented by lines between atoms. In hydroxylamine, \(NH_2 OH\):

• Each line (or bond) consists of a pair of shared electrons.
• Nitrogen forms covalent bonds with two hydrogen atoms and one oxygen atom.
• Oxygen shares electrons with both nitrogen and an additional hydrogen atom.

Forming these covalent bonds helps each atom achieve a stable electron configuration, usually aligning with the octet rule. Covalent bonding is a cornerstone of molecular structures and dictates the physical properties and reactivity of a substance.

Exploring Electronegativity

Electronegativity is a chemical property that describes how strongly an atom can attract a bonding pair of electrons. It plays a critical role in determining the type and nature of chemical bonds.Atoms with higher electronegativity values will draw electrons closer, which can lead to the formation of polar bonds if there's a significant difference between the atoms involved.
In hydroxylamine \(NH_2 OH\):

• Oxygen is more electronegative than nitrogen and significantly more than hydrogen.
• This results in a polar covalent bond between oxygen and the atoms it connects with, where shared electrons spend more time closer to the oxygen atom.
• Such differences affect the molecule’s physical properties like solubility and boiling point.

Understanding electronegativity is essential in predicting how molecules behave, their interactions with other substances, and how atoms within a molecule relate to each other.