Question

How do you know which side of a polar bond has the partial positive charge? Identify the positively charged side of each polar bond. a) \(\mathrm{H}-\mathrm{Cl}\) b) \(\mathrm{N}\) -F

Short answer

In H-Cl, H is partially positive; in N-F, N is partially positive.

Step-by-step solution

Understanding Polar Bonds

A polar bond is formed when two atoms have different electronegativities, causing an uneven distribution of electrons. The more electronegative atom pulls the bonding electrons closer, giving it a partial negative charge, while the less electronegative atom acquires a partial positive charge.

Checking Electronegativity Difference for H-Cl

Look at the electronegativities of hydrogen and chlorine. Chlorine is more electronegative than hydrogen. Therefore, electrons are pulled towards chlorine, making chlorine partially negative and hydrogen partially positive.

Identifying the Partial Positive Charge in H-Cl

In the polar bond \( ext{H-Cl}\), hydrogen ( ext{H}) is less electronegative than chlorine ( ext{Cl}), hence \( ext{H}\) has a partial positive charge.

Checking Electronegativity Difference for N-F

Now examine the electronegativities of nitrogen and fluorine. Fluorine is more electronegative than nitrogen, thus attracting the electrons more strongly and gaining a partial negative charge.

Identifying the Partial Positive Charge in N-F

In the polar bond \( ext{N-F}\), nitrogen ( ext{N}) is less electronegative compared to fluorine ( ext{F}), leading to nitrogen having a partial positive charge.

Key concepts

Electronegativity

Electronegativity is a key concept in understanding how atoms bond with each other. It's a measure of how strongly an atom attracts electrons when it's in a compound. This property varies across the periodic table:

• Elements on the right side tend to have higher electronegativities because they want to gain electrons to complete their outer shells.
• Conversely, elements on the left tend to have lower electronegativities since they more readily lose electrons.

For example, chlorine has a high electronegativity compared to hydrogen, hence in a hydrogen chloride (H-Cl) bond, chlorine will attract more electrons towards itself. This results in an unequal sharing of electrons, creating a dipole in the bond.

To consider electronegativity in terms of bond polarity, it's important to note that the greater the difference in electronegativity between two bonded atoms, the more polar the bond will be.

Partial Positive Charge

In a polar bond, the atom with the lower electronegativity will typically end up with a partial positive charge. This happens because it shares electrons with an atom that pulls them closer due to higher electronegativity. Let's think about why this occurs:

• Electrons carry a negative charge, so when an atom loses access to them, it becomes partially positive.
• This situation arises when the more electronegative atom pulls the electron density away.

For instance, in the N-F bond (nitrogen-fluoride), nitrogen is less electronegative than fluorine. Thus, nitrogen ends up with a partial positive charge as fluorine attracts the shared electrons closer. This shift creates areas of partial positivity and negativity, crucial for the interaction of molecules.

Bond Polarity

Bond polarity occurs when the difference in electronegativity between two bonded atoms leads to an unequal sharing of electrons. This usually results in one side of the molecule having a partial negative charge and the other side having a partial positive charge. Understanding bond polarity involves several aspects:

• The electronegativity difference: A greater difference means a more polar bond.
• The partial charges: Created due to the electron distribution favoring the more electronegative atom.
• The direction of the dipole: The stronger pull to one side creates a dipole moment.

Taking H-Cl and N-F as examples, both have noticeable bond polarity due to significant differences in the electronegativities of their constituent atoms. Chlorine and fluorine, being the more electronegative elements, acquire partial negative charges, while hydrogen and nitrogen are left with partial positive charges, resulting in polar bonds. These bonds contribute to the molecules’ physical properties, such as boiling points and solubility.