Question

An oxygen atom can bond to a HBrO molecule to give \(\mathrm{HBrO}_{2} .\) Draw the electron dot formula for \(\mathrm{HBrO}_{2}\) and label a coordinate covalent bond.

Short answer

The electron dot structure for HBrO2 shows H-O-Br=O, with a coordinate covalent bond between Br and O.

Step-by-step solution

Draw the Lewis structure for HBrO

Begin by drawing the electron dot formula for the initial molecule, HBrO. Hydrogen (H) will form a single bond with oxygen (O), so place hydrogen next to oxygen. Oxygen, while having six valence electrons, will share two pairs - one with hydrogen to form H-O bond and two lone pairs. Bromine (Br), with seven valence electrons, will form a single bond with oxygen: H-O-Br, with two lone pairs on both oxygen and bromine.

Add the Second Oxygen Atom

Incorporate the second oxygen atom into the structure. Oxygen has six valence electrons and is inclined to form two bonds to fulfill its octet. Attach this oxygen to supplement a bond with Bromine. The structure becomes H-O-Br-O, where each oxygen prefers to have a complete octet, requiring changes in bonding.

Form a Coordinate Covalent Bond

To address the octet rule, use a coordinate covalent bond between Bromine and the second Oxygen. A coordinate covalent bond occurs when both electrons in the bond come from one atom. The second Oxygen, having excess electrons, donates a pair of electrons to form a bond with Bromine. Ensure all atoms maintain their valency requirements.

Finalize the Electron Dot Structure

Ensure each atom satisfies the octet rule where possible. Hydrogen (1) connects to Oxygen (2), which connects to Bromine (single bond) and finally to the second Oxygen with a double bond, where the second bond is coordinate covalent. Add lone pairs to each of the oxygen atoms where needed to satisfy octet configurations: H-O-Br=O, with the double bond being coordinate covalent.

Key concepts

Coordinate Covalent Bond

A coordinate covalent bond is a special type of covalent bond where both of the shared electrons in the bond come from one of the two atoms involved. This differs from a typical covalent bond, where each atom donates one electron to the bond. To make this concept clear, imagine a pair of electrons that one atom has, but instead of keeping them both to itself, it shares them with another atom that needs electrons.

In the exercise you worked on, this bond is critical in the formation of the HBrO_2 molecule. The second oxygen atom, having extra electrons, forms a coordinate covalent bond with bromine. This means the oxygen atom donates a pair of its own electrons to create a bond with bromine, which helps complete the structural arrangement needed to satisfy both atoms.

Key points about coordinate covalent bonds include:

• Only one atom provides both electrons for the bond.
• The bond acts like any other covalent bond, once formed.
• It helps fill electron shells and satisfies certain bonding requirements.

Electron Dot Formula

Electron dot formulas are visual representations of the valence electrons in chemical molecules. They are also known as Lewis structures. These diagrams use dots to symbolize the electrons and can show how these electrons are arranged in a molecule and how they contribute to bonding.

For example, when drawing the electron dot formula for HBrO_2, each dot represents an electron associated with the atoms: hydrogen, bromine, and the two oxygens. This structure helps visualize how electrons are shared between atoms to form bonds, and which atoms might have extra electrons or need more to be stable.

Creating an accurate electron dot formula involves:

• Counting valence electrons for each atom involved in the molecule.
• Assigning electrons to represent bonds or lone pairs according to the molecule's geometry.
• Checking that the molecule respects the octet rule when possible.

Lewis structures are useful for predicting the reactivity, shapes, and properties of molecules.

Octet Rule

The octet rule is a principle in chemistry that atoms tend to bond in such a way that they each achieve a full outer shell of eight electrons, similar to a noble gas. This rule is a guideline that helps explain why certain molecules form in the way that they do.

Not all elements strictly follow the octet rule, such as in the case of hydrogen, which is stable with just two electrons.

In HBrO_2, the octet rule guides the distribution of electrons between hydrogen, bromine, and oxygen atoms to form stable bonds. Oxygen naturally has six valence electrons and seeks to bond with other atoms so that it can reach an octet. When forming HBrO_2, each oxygen aims to be surrounded by eight electrons in total (counting shared and lone pairs).

Important aspects of the octet rule are:

• Atoms form molecules to attain a noble gas-like electron configuration.
• It predicts the ways atoms will bond and which electron constellations are stable.
• Even elements that do not strictly obey the octet rule, like bromine, still engage in bonding for stability.

The octet rule is an essential tool for understanding molecular structures, stability, and chemical reactivity.