Question

Using the symbols \(\delta-\) and \(\delta+\), indicate the direction of polarity in each polar covalent bond. (a) \(\mathrm{C}-\mathrm{N}\) (b) \(\mathrm{N}-\mathrm{O}\) (c) \(\mathrm{C}-\mathrm{Cl}\)

Short answer

Question: Determine the direction of polarity for the following polar covalent bonds using the symbols \(\delta-\) and \(\delta+\): (a) C-N, (b) N-O, (c) C-Cl. Answer: (a) C(\(\delta+\)) - N(\(\delta-\)), (b) N(\(\delta+\)) - O(\(\delta-\)), (c) C(\(\delta+\)) - Cl(\(\delta-\)).

Step-by-step solution

Determine electronegativity values of the atoms involved in each bond

Using a periodic table or an electronegativity table, look up the electronegativity values of the following elements: C, N, O, and Cl.

Compare electronegativity values for each bond

For each given bond (C-N, N-O, and C-Cl), compare the electronegativity values of the atoms involved. The atom with higher electronegativity will have the partial negative charge (\(\delta-\)), while the atom with lower electronegativity will have the partial positive charge (\(\delta+\)).

Indicate the direction of polarity in each bond

(a) For the C-N bond, since the electronegativity of N is greater than that of C, the bond polarity will be C(\(\delta+\)) - N(\(\delta-\)). (b) For the N-O bond, since the electronegativity of O is greater than that of N, the bond polarity will be N(\(\delta+\)) - O(\(\delta-\)). (c) For the C-Cl bond, since the electronegativity of Cl is greater than that of C, the bond polarity will be C(\(\delta+\)) - Cl(\(\delta-\)).

Key concepts

Electronegativity

Electronegativity is a measure of how strongly an atom attracts electrons towards itself. This property is crucial in determining how atoms form bonds with each other. When two atoms form a bond, the electrons are shared between them. However, they are not always shared equally.

• An atom with higher electronegativity will attract the shared electrons more strongly.
• The periodic table can help us find the electronegativity values of elements. Generally, electronegativity increases as you move from left to right across a period and decreases as you move down a group.

When comparing atoms such as carbon (C), nitrogen (N), oxygen (O), and chlorine (Cl), we note the following trends:

• Nitrogen is more electronegative than carbon.
• Oxygen is more electronegative than nitrogen.
• Chlorine is more electronegative than carbon.

These differences help predict which atom in a bond carries a partial negative charge, which we'll explore next.

Bond Polarity

Bond polarity arises from the difference in electronegativity values between two atoms in a covalent bond. When electrons are shared between different atoms, their unequal sharing can create a polar covalent bond. In a polar covalent bond, the atom with the higher electronegativity gets a bit more control over the shared electrons. This creates a bond where one end is more negative, and the other more positive. For example:

• For a Carbon-Nitrogen (C-N) bond, nitrogen is more electronegative and pulls electrons closer, making C (\( \delta^+ \)) and N (\( \delta^- \)).
• In a Nitrogen-Oxygen (N-O) bond, oxygen attracts electrons more strongly than nitrogen does, creating N (\( \delta^+ \)) and O (\( \delta^- \)).
• With a Carbon-Chlorine (C-Cl) bond, chlorine has higher electronegativity than carbon, resulting in C (\( \delta^+ \)) and Cl (\( \delta^- \)).

This concept is important as it helps us understand molecule shapes and reactivity, influencing how molecules interact with each other.

Partial Charges

Partial charges are essential outcomes of polar covalent bonds. They occur due to the uneven distribution of electrons between the two atoms involved. This leads to one atom having a tiny negative charge and the other a tiny positive charge.

• The symbol \( \delta^+ \) indicates a partial positive charge, showing the atom is slightly electron-poor.
• The symbol \( \delta^- \) indicates a partial negative charge, showing the atom is slightly electron-rich.

Partial charges play a critical role in many chemical processes, such as solubility in water, forming hydrogen bonds, and participating in chemical reactions. Understanding where these charges are can help predict the behavior of molecules in various environments, explaining why certain substances dissolve in water, while others do not, or how proteins fold into their functional three-dimensional structures.