Question

An oxygen atom can bond to a hydrogen bromide molecule to give \(\mathrm{HBrO}\). Draw the electron dot formula for \(\mathrm{HBrO}\) and label a coordinate covalent bond.

Short answer

Oxygen forms a coordinate covalent bond with hydrogen using a lone pair.

Step-by-step solution

Identify Valence Electrons

First, we need to determine the number of valence electrons for each element in the molecule \(\mathrm{HBrO}\). Hydrogen (H) has 1 valence electron, bromine (Br) has 7 valence electrons, and oxygen (O) has 6 valence electrons.

Total Number of Valence Electrons

Add the valence electrons from each atom to get the total for the molecule: \(1 + 7 + 6 = 14\). Therefore, \(\mathrm{HBrO}\) has a total of 14 valence electrons.

Draw Skeletal Structure

Start by arranging the atoms. Typically, hydrogen is on the end due to its ability to form only one single bond. To form \(\mathrm{HBrO}\), place H next to O, and then O next to Br, resulting in the sequence: H-O-Br.

Distribute Electrons

Put pairs of electrons between the atoms to form bonds: H-O-Br. Each bond uses 2 electrons. Thus, use 4 electrons for the two bonds. Now, 14 - 4 = 10 electrons remain to be distributed as lone pairs.

Complete Octet for Oxygen

Oxygen needs 8 electrons in total (including bonded electrons) to complete its octet. It already has 2 from the bond; provide the necessary 6 more as 3 lone pairs around O.

Complete Octet for Bromine

Bromine already has 2 electrons from the O-Br bond. Place the remaining 8 electrons as 4 lone pairs around Br to satisfy its octet. This completes its octet (7 inherent + 1 bond electron).

Identify Coordinate Covalent Bond

A coordinate covalent bond is formed when both electrons in a bond come from the same atom. In \(\mathrm{HBrO}\), this typically occurs between hydrogen and oxygen. The pair of electrons forming the donor bond comes from the lone pairs on oxygen, bonding with H.

Key concepts

Valence Electrons

In molecular chemistry, the concept of valence electrons is crucial. These are the electrons that reside in the outermost shell of an atom and participate in chemical bonds. Each element has a specific number of valence electrons, which influences how it bonds with other atoms.
For example, in the molecule \(\text{HBrO}\)
- Hydrogen (H) has 1 valence electron,
- Bromine (Br) has 7 valence electrons,
- Oxygen (O) has 6 valence electrons.
Understanding the valence electrons allows us to predict bonding possibilities and molecule stability. It helps determine how atoms will interact to form the molecule's structure. This is why the first step in constructing the electron dot formula is to identify and count the valence electrons. By doing so, we get a total of 14 valence electrons for the \(\text{HBrO}\) molecule.

Coordinate Covalent Bond

A coordinate covalent bond is a special type of covalent bond in which one atom donates both electrons to the bond. Unlike regular covalent bonds, where each atom provides one electron, the donor atom in a coordinate covalent bond supplies the entire electron pair.
In the case of \(\text{HBrO}\), oxygen forms a coordinate covalent bond with hydrogen. Oxygen not only shares its electrons but acts as a donor, creating a bond where both electrons come from its own valence shell. This occurs because oxygen is highly electronegative, making it capable of not just sharing but also donating its electron pair to form the bond.
Coordinate covalent bonds are important in understanding how electron-rich atoms like oxygen stabilize molecules by bonding with atoms that can accept an electron pair. These bonds are key to the unique properties and functions of various molecules.

Molecular Structure

The molecular structure describes how atoms are arranged in a molecule, defining its geometry and bonds. Drawing a molecule's structure gives us insight into how the atoms connect and where the electrons are located.
In constructing the electron dot structure of \(\text{HBrO}\), we begin with a skeletal structure that reflects the general bonding pattern. Here, hydrogen bonds to oxygen, which in turn bonds to bromine. This linear formation is typical:

• H-O-Br

The sequence reveals how the oxygen's high electronegativity causes it to form multiple bonds, including with hydrogen in a coordinate covalent bond.
The molecular structure also ensures that each atom satisfies the octet rule (or the duet for hydrogen), indicating full outer shells of electrons. In this structure, all remaining electrons are distributed as lone pairs to complete each atom's shell, highlighting areas of electron donation or electron sharing. This simple sketch of atom connectivity is vital for understanding both the physical properties and the reactivity of the molecule.