Question

Predict the type of bond (ionic, covalent, or polar covalent) one would expect to form between the following pairs of elements. a. \(\mathrm{Rb}\) and \(\mathrm{Cl}\) d. \(\mathrm{Ba}\) and \(\mathrm{S}\) b. \(S\) and \(S\) e. \(\mathrm{N}\) and \(\mathrm{P}\) c. \(C\) and \(\bar{F}\) f. \(\mathrm{B}\) and \(\mathrm{H}\)

Short answer

The bond types for each pair of elements are as follows: a. Rb and Cl: Ionic bond b. S and S: Covalent (nonpolar) bond c. C and F: Polar covalent bond d. Ba and S: Polar covalent bond e. N and P: Polar covalent bond f. B and H: Covalent (nonpolar) bond

Step-by-step solution

Write down the electronegativities of the given elements

Consult a periodic table or reference material to find the electronegativity values for the elements involved in each bond. Here are the values we'll need: Rb = 0.82, Cl = 3.16, Ba = 0.89, S = 2.58, N = 3.04, P = 2.19, C = 2.55, F = 3.98, B = 2.04, H = 2.20

Calculate the difference in electronegativity (DEN) between each pair

Using the electronegativity values, find the DEN for each given pair: a. Rb and Cl: |0.82 - 3.16| = 2.34 b. S and S: |2.58 - 2.58| = 0 c. C and F: |2.55 - 3.98| = 1.43 d. Ba and S: |0.89 - 2.58| = 1.69 e. N and P: |3.04 - 2.19| = 0.85 f. B and H: |2.04 - 2.20| = 0.16

Determine the bond type based on the DEN calculated

Now that we have the DEN values for each pair, we can determine the bond type: a. Rb and Cl: DEN = 2.34, which is greater than 1.7, so the bond is ionic. b. S and S: DEN = 0, which is less than 0.4, so the bond is covalent (nonpolar). c. C and F: DEN = 1.43, which is between 0.4 and 1.7, so the bond is polar covalent. d. Ba and S: DEN = 1.69, which is slightly less than 1.7, so the bond is polar covalent. e. N and P: DEN = 0.85, which is between 0.4 and 1.7, so the bond is polar covalent. f. B and H: DEN = 0.16, which is less than 0.4, so the bond is covalent (nonpolar). So, the bond types are as follows: a. Rb and Cl: Ionic bond b. S and S: Covalent (nonpolar) bond c. C and F: Polar covalent bond d. Ba and S: Polar covalent bond e. N and P: Polar covalent bond f. B and H: Covalent (nonpolar) bond

Key concepts

Ionic Bonds

When atoms transfer electrons from one to another, they form ionic bonds. This type of bond typically occurs between metals and non-metals. Atoms in ionic bonds have a significant difference in electronegativity, usually greater than 1.7.
For example, in the case of Rubidium (\( \mathrm{Rb} \)) and Chlorine (\( \mathrm{Cl} \)), the electronegativity difference is 2.34. This large difference causes Rubidium to lose an electron, which is then gained by Chlorine. The result is the formation of positively charged \( \mathrm{Rb}^+ \) and negatively charged \( \mathrm{Cl}^- \) ions.

• The positive and negative ions attract each other through electrostatic forces.
• These ions form a structured lattice, resulting in a stable compound.

The strength and stability of ionic bonds make them an essential concept in fields such as chemistry and material science.

Covalent Bonds

Covalent bonds form when two atoms share pairs of electrons. This type of bonding is most often found between non-metal atoms. When the electronegativity difference is less than 0.4, the bond is considered a nonpolar covalent bond.
An example is the bond between two sulfur atoms (\( \mathrm{S} \) and \( \mathrm{S} \)). With an electronegativity difference of 0, they share electrons equally. This equal sharing is characteristic of a covalent bond.

• Covalent bonds result in the formation of molecules.
• These bonds can be single, double, or triple, depending on the number of electron pairs shared.

Understanding covalent bonds helps explain how molecules form and behave, which is crucial in understanding organic chemistry.

Electronegativity

Electronegativity is a measure of an atom’s ability to attract and hold onto electrons when it is part of a compound. It's a key factor in determining the type of chemical bond that will form between atoms.
Differences in electronegativity values between atoms dictate whether a bond will be ionic, polar covalent, or covalent. For instance, when electronegativity differences are large (greater than 1.7), ionic bonds form. If the value is between 0.4 and 1.7, polar covalent bonds are created.

• Pauling scale is commonly used for measuring electronegativity.
• Fluorine has the highest electronegativity at 3.98, making it highly reactive.

Grasping electronegativity is important for predicting and understanding chemical behavior in reactions and compounds.

Polar Covalent Bonds

Polar covalent bonds are formed when atoms with an electronegativity difference between 0.4 and 1.7 share electrons unequally. This unequal sharing leads to a slight charge separation within the molecule, creating a dipole moment.
In the bond between carbon (\( \mathrm{C} \)) and fluorine (\( \mathrm{F} \)), the electronegativity difference is 1.43. This creates a polar covalent bond with a partial negative charge near fluorine and a partial positive charge near carbon.

• Polar bonds result in molecules with positive and negative poles.
• This property enables interactions with other polar compounds, such as water.

Polar covalent bonds are fundamental in chemistry because they affect the chemical and physical properties of molecules, such as solubility and boiling points.