Question

1. for each of the four molecules below, complete the following:

a. draw in the pair of electrons shared between atoms. draw the electrons closest to more electronegative atoms or in the middle of the bond if the atoms are equally electronegative.
b. for each atom, determine if it has any electrons that are shared unequally, if so, write a partial charge ($\delta+$ or $\delta -$) next to that atom.
c. label all polar bonds.
d. label each of the molecules below as polar or nonpolar.

1. label the following molecules as polar or nonpolar.

Explanation:

Molecule 1: Ethane ($C_2H_6$)

Step1: Electron - sharing

Carbon - carbon and carbon - hydrogen bonds are non - polar or have very small electronegativity differences. Draw the shared electron pairs between atoms. C - C and C - H bonds have electrons shared relatively evenly.

Step2: Partial charges

Since electronegativity differences are small, no significant partial charges ($\delta+$ or $\delta-$) on atoms.

Step3: Polar bonds

No polar bonds as electronegativity differences are minimal.

Step4: Molecule polarity

Non - polar molecule as there is no net dipole moment due to symmetric distribution of charge.

Molecule 2: Carbon dioxide ($CO_2$)

Step1: Electron - sharing

In $C = O$ bonds, electrons are drawn closer to oxygen due to higher electronegativity of oxygen.

Step2: Partial charges

Carbon has a partial positive charge ($\delta+$) and oxygen has a partial negative charge ($\delta-$) in the $C = O$ bonds.

Step3: Polar bonds

$C = O$ bonds are polar.

Step4: Molecule polarity

Non - polar molecule because the linear shape of $CO_2$ results in the cancellation of the bond dipoles.

Molecule 3: Methanol ($CH_3OH$)

Step1: Electron - sharing

In C - H bonds, electrons are shared somewhat evenly, but in C - O and O - H bonds, electrons are drawn closer to oxygen.

Step2: Partial charges

Carbon in C - O has $\delta+$, oxygen in C - O and O - H has $\delta-$, and hydrogen in O - H has $\delta+$.

Step3: Polar bonds

C - O and O - H bonds are polar.

Step4: Molecule polarity

Polar molecule due to the presence of polar bonds and an asymmetric shape.

Molecule 4: Water ($H_2O$)

Step1: Electron - sharing

In O - H bonds, electrons are drawn closer to oxygen.

Step2: Partial charges

Oxygen has $\delta-$ and hydrogen has $\delta+$.

Step3: Polar bonds

O - H bonds are polar.

Step4: Molecule polarity

Polar molecule due to its bent shape and the presence of polar O - H bonds.

Molecule 5: Oxygen ($O_2$)

Step1: Electron - sharing

Electrons are shared equally between two oxygen atoms.

Step2: Partial charges

No partial charges as electronegativity of both atoms is the same.

Step3: Polar bonds

No polar bonds.

Step4: Molecule polarity

Non - polar molecule.

Molecule 6: Methylamine ($CH_3NH_2$)

Step1: Electron - sharing

In C - H bonds, electrons are shared somewhat evenly, in C - N and N - H bonds, electrons are drawn closer to nitrogen.

Step2: Partial charges

Carbon in C - N has $\delta+$, nitrogen in C - N and N - H has $\delta-$, and hydrogen in N - H has $\delta+$.

Step3: Polar bonds

C - N and N - H bonds are polar.

Step4: Molecule polarity

Polar molecule due to the presence of polar bonds and an asymmetric shape.

Molecule 7: Acetic acid ($CH_3COOH$)

Step1: Electron - sharing

In C - H bonds, electrons are shared somewhat evenly, in C - C, C = O, C - O and O - H bonds, there are different electron - sharing patterns with electrons drawn closer to more electronegative atoms (Oxygen).

Step2: Partial charges

Carbon in C - C has a relatively neutral charge, carbon in C = O has $\delta+$, oxygen in C = O and C - O and O - H has $\delta-$, hydrogen in O - H has $\delta+$.

Step3: Polar bonds

C = O, C - O and O - H bonds are polar.

Step4: Molecule polarity

Polar molecule due to the presence of polar bonds and an asymmetric shape.

Answer:

Ethane: Non - polar; Carbon dioxide: Non - polar; Methanol: Polar; Water: Polar; Oxygen: Non - polar; Methylamine: Polar; Acetic acid: Polar