Question

Which of the following statements is false concerning bonding? Elements with extremely different electronegativities tend to form ionic bonds with each other. b. In an \(\mathrm{N}-\mathrm{O}\) bond, electron density is greater near the \(\mathrm{O}\) atom. c. An \(\mathrm{N}-\mathrm{O}\) bond is an example of a polar covalent bond. d. In general, chemical bonds form to minimize energy. e. The bond in \(\mathrm{KBr}\) is formed by sharing electrons.

Short answer

The false statement concerning chemical bonding is: "The bond in \(\mathrm{KBr}\) is formed by sharing electrons." The bond in \(\mathrm{KBr}\) is ionic, resulting from the transfer of an electron from potassium to bromine, not by sharing electrons.

Step-by-step solution

1. Analyzing Statement a

Elements with extremely different electronegativities tend to form ionic bonds with each other. This statement is true because, in ionic bonding, one atom donates an electron to another atom with a higher electronegativity, resulting in positively and negatively charged ions that attract each other forming an ionic bond.

2. Analyzing Statement b

In an \(\mathrm{N}-\mathrm{O}\) bond, electron density is greater near the \(\mathrm{O}\) atom. This statement is true since oxygen has a higher electronegativity than nitrogen, meaning that it attracts the shared electrons in the bond more strongly, resulting in greater electron density near the oxygen atom.

3. Analyzing Statement c

An \(\mathrm{N}-\mathrm{O}\) bond is an example of a polar covalent bond. This statement is also true. In a polar covalent bond, atoms with different electronegativities share electrons but not equally. Since the electronegativities of nitrogen and oxygen are different, they form a polar covalent bond.

4. Analyzing Statement d

In general, chemical bonds form to minimize energy. This statement is true. Chemical bond formation leads to a lower energy state for the atoms involved, making the resulting molecule more stable. The lower energy state is achieved by sharing, gaining, or losing electrons depending on the type of bond formed.

5. Analyzing Statement e

The bond in \(\mathrm{KBr}\) (potassium bromide) is formed by sharing electrons. This statement is false. In \(\mathrm{KBr}\), potassium (K) has one valence electron while bromine (Br) has seven valence electrons. Due to the difference in their electronegativities, potassium donates its valence electron to bromine, resulting in an ionic bond. In this case, electrons are not shared but instead transferred, forming oppositely charged ions.

Key concepts

Ionic Bonding

Ionic bonding is a type of chemical bond where atoms transfer electrons to achieve stability. This occurs between elements with significantly different electronegativities.
Electronegativity is the tendency of an atom to attract electrons. In ionic bonding, one atom becomes a positive ion, known as a cation, by losing an electron, while the other becomes a negative ion, called an anion, by gaining an electron.
This electron transfer results in a strong electrostatic attraction between the oppositely charged ions, forming a stable ionic bond.

• Typically occurs between metals and non-metals.
• Leads to the formation of crystalline solids like sodium chloride (NaCl).
• Ionic compounds generally have high melting and boiling points due to the strong attractions between ions.

Electronegativity

Electronegativity refers to the ability of an atom to attract shared electrons in a chemical bond.
The concept of electronegativity is crucial for understanding different types of bonds, especially when distinguishing between ionic and covalent bonds.
When the difference in electronegativity between two atoms is very large, ionic bonds are likely to form. However, smaller differences result in covalent bonds.

• Measured on the Pauling scale, which assigns fluorine the highest value of 4.0.
• Noble gases generally are not assigned electronegativity values because they rarely form compounds.
• Understanding differences in electronegativity helps predict molecular structure and bond polarity.

Polar Covalent Bond

In polar covalent bonds, electrons are shared between atoms, but the sharing is unequal due to differences in electronegativity.
These bonds result in regions of partial positive and negative charges within a molecule, giving rise to a dipole moment.
The asymmetric distribution of electron density creates polarity in the molecule, affecting properties such as solubility and intermolecular forces.

• An example is the bond between nitrogen and oxygen, where oxygen is more electronegative.
• Water ( H_2O ) is another classic example, making it a polar molecule due to its bent shape and polar covalent bonds.
• Polar molecules interact through dipole-dipole forces and hydrogen bonding.

Electron Density

Electron density describes the probability of finding electrons in a particular region around an atom or within a molecule.
Higher electronegativity means an atom is more efficient at pulling electron density towards itself, affecting the bond type and molecular shape.
In covalent bonds, especially polar ones, electron density is often unevenly distributed, leading to molecular polarity.

• Visualized using electron density maps and molecular models.
• Influences the reactivity and interaction of molecules with others.
• Important in resonant structures, where the electron density can be delocalized over multiple atoms.