Question

Which element-element bond has the highest bond energy? (a) \(\mathrm{SiF}_{4}\) (b) Si-Si (c) \(\mathrm{Sn}-\mathrm{Sn}\) (d) Ge-Ge

Short answer

(a) SiF element{4} has the highest bond energy due to strong Si-F bonds.

Step-by-step solution

Understanding Bond Energy

Bond energy is the measure of the bond strength in a chemical bond. The higher the bond energy, the more energy it takes to break the bond. Stronger bonds involve smaller atoms and higher electronegativity differences.

Analyzing Each Option

Evaluate each given bond: - \(\text{(a) Si-F in SiF}_4\,\) has strong Si-F bonds, given the high electronegativity of F.- \(\text{(b) Si-Si}\,\) is a bond between two silicon atoms of similar atomic size and lower bond energy than Si-F. - \(\text{(c) Sn-Sn}\,\) involves larger atoms with weak metallic bonds.- \(\text{(d) Ge-Ge}\,\) involves two germanium atoms, larger than Si but smaller than Sn.

Comparing Bond Strengths

The Si-F bond in \(\text{SiF}_4\,\) is a polar covalent bond with high bond energy due to the significant electronegativity difference and smaller atomic size. In contrast, Si-Si, Sn-Sn, and Ge-Ge bonds are nonpolar covalent bonds with larger atomic sizes, leading to weaker bonds.

Conclusion

The Si-F bond in \(\text{SiF}_4\,\) has the highest bond energy of the options provided, due to its strong polar covalent nature, compared to the weaker nonpolar covalent bonds of the homonuclear elements. Therefore, (a) \(\text{SiF}_4\,\) is the correct answer.

Key concepts

Polar Covalent Bonds

In chemistry, polar covalent bonds are fascinating interactions where two atoms share their outer electrons, but not equally. When bond partners have different abilities to attract these electrons, the bond becomes polar. This uneven sharing of electrons leads to one atom having a partial negative charge and the other, a partial positive charge. Imagine it like a team of two in a tug-of-war, pulling on the electron cloud. The atom with greater 'pulling power' - measured by an attribute called electronegativity - attracts the electron cloud more towards itself. Take, for instance, a bond like Si-F in SiF₄. Here, fluorine outshines silicon in electronegativity, causing the bond to be polar. This results in a situation where the fluorine holds more of the electron density, introducing a dipole that contributes to stronger bond characteristics. Consequently, such polar covalent bonds often exhibit high bond energies as seen in SiF₄, due to this marked difference in electron pulling strength.

Electronegativity Differences

Electronegativity is a key concept that explains how atoms in a molecule share electrons. It's like the atom's charismatic personality that determines its ability to attract electrons in a bond. Different atoms have different electronegativities, and when these values vary greatly, the result is usually a polar covalent bond. Let's delve into what these differences mean. When two bonded atoms have a significant electronegativity difference, the bond becomes polar, as seen in Si-F bonds. The disparity allows for a shift in electron density towards the more electronegative atom. This generates a partial positive charge on one atom and a partial negative charge on the other. Electronegativity differences contribute significantly to bond energy, helping predict a molecule's behavior and reactivity. Greater differences typically lead to stronger bonds, making molecules like SiF₄ quite stable, due to strong polar bonds caused by the lead role of electronegativity differences.

Nonpolar Covalent Bonds

Nonpolar covalent bonds occur when two atoms with similar electronegativities share their electrons equally. This mutual sharing, without either taking more than their fair share, results in a balanced distribution of electron density. It's a peaceful alliance where no atom hogs the electrons more than the other. Consider homonuclear bonds like Si-Si, Sn-Sn, or Ge-Ge. Each comprises identical atoms, meaning their electronegativities, and by extension, their electron pulling power, are identical. Consequently, there's no charge separation across the bond, making it nonpolar. These bonds tend to have lower bond energies compared to polar covalent bonds. That's because there is less force holding the atoms together, making them relatively weaker and more reactive under certain conditions. Understanding nonpolar covalent bonds enlightens us about the stability and reactivity of different substances in which these bonds occur.