Question

Write the electron-dot structure for the covalent compound ethane, \(\mathrm{C}_{2} \mathrm{H}_{6}\).

Short answer

The electron-dot structure shows each carbon bonded to three hydrogens and one single bond between the carbons.

Step-by-step solution

Understand the Molecular Structure

Ethane ( \( \mathrm{C}_{2} \mathrm{H}_{6} \) is a simple alkane with two carbon atoms and six hydrogen atoms. Each carbon atom forms four single bonds, typical for alkanes, with three bonds connecting to hydrogen atoms and one to another carbon atom.

Determine Total Valence Electrons

Carbon has 4 valence electrons, and hydrogen has 1 valence electron. With two carbon atoms and six hydrogen atoms, the total number of valence electrons is \( 2 \times 4 + 6 \times 1 = 14 \).

Arrange Atoms and Create Bonds

Place the two carbon atoms in the center, and connect them with a single bond (using two electrons). Arrange the hydrogen atoms around the carbon atoms, with each hydrogen forming a single bond to a carbon. Each bond uses 2 electrons.

Distribute Remaining Electrons

Place the remaining electrons to satisfy the octet rule for carbon. After forming all necessary single bonds with hydrogen, carbon should satisfy its tetravalency (4 bonds or 8 shared electrons) with three bonds with hydrogen and one with the other carbon.

Verify Electron Count

Verify that all 14 valence electrons have been used: 3 bonds for each carbon with hydrogen (6 total bonds each accounting for 2 electrons), and 1 bond between the carbons. This totals 14 electrons, which matches the number of available valence electrons.

Key concepts

Electron-Dot Structure

The electron-dot structure is a valuable tool in studying chemical bonding. It provides a visual way to represent the valence electrons in an atom, molecule, or compound.
For ethane (\( \mathrm{C}_{2} \mathrm{H}_{6} \)), the electron-dot structure showcases how each atom interacts through shared electrons.
In the electron-dot structure of ethane, each carbon atom is shown bonded to three hydrogen atoms and one carbon atom. This representation uses dots to symbolize the electrons and lines drawn between atoms to indicate shared pairs forming a covalent bond.
By creating a diagram, you illustrate the connections between atoms and how they achieve stable configurations that often resemble the closest noble gases.

Valence Electrons

Valence electrons are the outermost electrons of an atom. They are crucial in forming chemical bonds since they are involved in interactions with other atoms.
Each element's valence electrons determine its chemical reactivity and bonding behavior. For instance, carbon, with its four valence electrons, tends to form four bonds to satisfy its need for a full valence shell.
In ethane (\(\mathrm{C}_{2}\mathrm{H}_{6}\)), the total number of valence electrons is 14.

• Each carbon atom contributes 4 electrons (as it is in group 14 of the periodic table).
• Each hydrogen atom brings 1 valence electron.

These valence electrons join together to form single covalent bonds, creating a stable compound.

Lewis Structures

Lewis structures are diagrams that show the bonding between atoms and the lone pairs of electrons in a molecule.
They are critical for visualizing the electron configuration within a molecule and understanding how the atoms interact in a chemical bond.
For ethane, Lewis structures present the hydrogen and carbon atoms connected; each line (or pair of dots) between atoms represents a pair of shared electrons (or a covalent bond).
Here, ethane's structure includes:

• Each of the two carbon atoms sharing an electron pair with another carbon through a single line.
• Each hydrogen atom forms a single bond with one of the carbon atoms, depicted by a single line.

Such diagrams confirm that all atoms achieve the desired electron configuration conforming to common bonding principles.

Octet Rule

The octet rule is a key principle in explaining chemical bonding. It states that atoms tend to bond in such a way that each has eight electrons in its valence shell, emulating the electron configuration of noble gases.
Carbon atoms in ethane follow this rule by sharing electrons to form covalent bonds that fill their outer shell to yield a total of eight electrons.
Hydrogen is an exception, as it only requires two electrons for a complete outer shell, much like helium. In ethane, each carbon shares its four valence electrons through one carbon-carbon bond and three carbon-hydrogen bonds.
Thus, the octet rule helps explain the arrangement and stability of atoms within ethane and similar compounds.