Question

The number and type of bonds between two carbon atoms in calcium carbide are: (a) One sigma, two pi (b) Two sigma, two pi (c) One sigma, one pi (d) Two sigma, one pi

Short answer

(a) One sigma, two pi

Step-by-step solution

Understanding Calcium Carbide

Calcium carbide is a compound with the chemical formula CaC₂. It consists of a calcium ion ext{Ca}^{2+} and a carbide ion ext{C}_2^{2-}. The carbide ion is the focus in identifying the bond types between the carbon atoms.

Analyzing the Carbide Ion

The carbide ion, ext{C}_2^{2-}, consists of two carbon atoms sharing electrons. To determine the bond types, we must understand the structure. This ion has a triple bond connecting the two carbon atoms.

Identifying the Bonds in a Triple Bond

A triple bond between two carbon atoms typically consists of one sigma (σ) bond and two pi (π) bonds. The sigma bond is formed by the head-to-head overlap of two sp hybrid orbitals, while the two pi bonds are formed by the lateral overlap of the unhybridized p orbitals.

Selecting the Correct Answer

Based on the analysis, the two carbon atoms in calcium carbide are connected by one sigma bond and two pi bonds, corresponding to a triple bond's structure.

Key concepts

Calcium Carbide

Calcium carbide is an interesting compound with the chemical formula \( \text{CaC}_2 \). Its structure is composed of a calcium ion \( \text{Ca}^{2+} \) and a carbide ion \( \text{C}_2^{2-} \). The carbide ion is what interests chemists because it showcases a unique bonding between its two carbon atoms. These carbon atoms are connected in such a way that they have a triple bond between them. The presence of such a bond shows the connection through shared electrons, offering insight into the molecule's strength and reactivity.

Calcium carbide is used extensively in industry. It is most famously known for its role in producing acetylene gas when it reacts with water. This reaction is essential in creating a flame hot enough for welding. Understanding its bonding is key to appreciating its reactive nature and practical applications.

Sigma and Pi Bonds

When delving into chemical bonding, 'Sigma and Pi' bonds are fundamental concepts. The sigma (\( \sigma \)) bond is the backbone of molecular structures. It is formed by the end-to-end overlap of atomic orbitals, typically involving \( sp, sp^2, \) or \( sp^3 \) hybrid orbitals when it involves carbon atoms. Sigma bonds allow for the free rotation of bonded atoms around the bond axis, contributing to the stability of linear structures.

The pi (\( \pi \)) bonds are different. They arise from the side-by-side overlap of p-orbitals. Each pi bond contributes to the overall bond strength, but they do not allow for rotation like sigma bonds. Instead, pi bonds add rigidity to the structure, which is evident in the locked arrangement of bonded atoms.

• Sigma bonds can occur alone, but pi bonds will always accompany an existing sigma bond.
• Sigma bonds are stronger due to their direct overlap, while pi bonds add additional interactions.

Understanding both sigma and pi bonds is essential for appreciating the complexity of molecular shapes and reactivity.

Triple Bonds

In chemical bonding, a triple bond is one of the strongest bonds found between atoms, often involving carbon-to-carbon connections. A hallmark of a triple bond is that it is comprised of one sigma bond and two pi bonds. The sigma bond arises from the head-on overlapping of orbitals, while the pi bonds result from the lateral overlapping of the remaining p orbitals.

This configuration lends the triple bond its characteristic strength and short bond length, which contributes to the rigidity and stability of molecules containing them. Triple bonds, often seen in alkynes, limit the rotation around the bond, leading to a very linear shape. Such linear structures are brilliant examples of molecular simplicity.

It's critical to note the following about triple bonds:

• Triple bonds drastically increase molecular stability and affect the compound's boiling and melting points.
• They are less reactive than single and double bonds due to this added stability but require more energy to break.

By grasping the significance of triple bonds, one can better understand the importance of molecular geometry and bonding interactions in chemistry.