Q. \( \mathrm{C_8H_{18}} \) Lewis structure.

Let’s interpret the request carefully: you are asking for the Lewis structure of \( \mathrm{C_8H_{18}} \). This formula corresponds to a saturated hydrocarbon (an alkane). The Lewis structure you want is the connectivity of all atoms and the placement of all valence electrons as dots/lines.

Because \(\mathrm{C_8H_{18}}\) is an alkane, in the context of Lewis structures, the key structural fact is that it contains only single bonds between carbons, and each carbon has enough hydrogens to “fill” its typical four bonds (tetravalent carbon).

Step 1: Identify the molecular type

\(\mathrm{C_8H_{18}}\) matches the general formula for alkanes:

\[
\mathrm{C_nH_{2n+2}}
\]
For \(n=8\):

\[
\mathrm{H} = 2(8)+2 = 18
\]
So \(\mathrm{C_8H_{18}}\) is an alkane.

Step 2: Choose a reasonable Lewis structure connectivity

Multiple constitutional isomers exist for \(\mathrm{C_8H_{18}}\) (octane has several isomers). The most common and simplest to draw in Lewis-structure problems is n-octane:

\[
\mathrm{CH_3-(CH_2)_6-CH_3}
\]

This describes a straight chain of 8 carbons with single bonds between adjacent carbons.

Step 3: Count how many hydrogens each carbon has

In a straight-chain alkane:

• The two end carbons are bonded to only one other carbon, so each end carbon has 3 hydrogens (it is \(\mathrm{CH_3}\)).

• The six middle carbons are each bonded to two other carbons, so each middle carbon has 2 hydrogens (each is \(\mathrm{CH_2}\)).

Check hydrogen count:

\[
2(3) + 6(2) = 6 + 12 = 18
\]
Matches \(\mathrm{C_8H_{18}}\). Good.

Step 4: Build the Lewis structure using single bonds

Lewis structures for hydrocarbons typically show:

• \(\mathrm{C-C}\) bonds as single lines (one shared pair of electrons).

• \(\mathrm{C-H}\) bonds as single lines.

For n-octane, the skeletal connectivity is:

\[
\mathrm{H_3C-CH_2-CH_2-CH_2-CH_2-CH_2-CH_2-CH_3}
\]
This is the Lewis-structure connectivity of all atoms using single bonds only.

Step 5: Show the hydrogen count on each carbon explicitly

Write it as a fully specified chain:

\[
\mathrm{CH_3-CH_2-CH_2-CH_2-CH_2-CH_2-CH_2-CH_3}
\]

Step 6: Electron (dot) placement note

In a Lewis structure, carbon has four valence electrons and forms four single covalent bonds. Each hydrogen has one valence electron and forms one single covalent bond.

So every bond shown above corresponds to a shared pair of electrons:

• Each \(\mathrm{C-H}\) bond contains one shared electron pair.

• Each \(\mathrm{C-C}\) bond contains one shared electron pair.

There are no lone pairs on carbon or hydrogen in a saturated alkane Lewis structure (because all valence electrons are used in bonding).

Final Lewis structure (n-octane form)

Lewis structure connectivity:

\[
\mathrm{CH_3-CH_2-CH_2-CH_2-CH_2-CH_2-CH_2-CH_3}
\]

This corresponds to an alkane Lewis structure for \(\mathrm{C_8H_{18}}\) (specifically the straight-chain isomer n-octane).