Question

Carbon tetrachloride does have not dipole moment because of (a) its planar structure (b) its regular tetrahedral structure (c) similar sizes of carbon and chlorine atoms (d) similar electron affinities of carbon and chlorine

Short answer

The correct answer is (b) its regular tetrahedral structure.

Step-by-step solution

Understand Dipole Moment

A dipole moment occurs when there is a separation of positive and negative charges in a molecule, resulting in a molecule with a partial positive end and a partial negative end. To have no dipole moment, the molecule must be symmetrical in such a way that any polarities within the molecule cancel each other out.

Analyze Carbon Tetrachloride (CCl4) Structure

Carbon tetrachloride (CCl4) consists of one carbon atom bonded to four chlorine atoms. The structure must be examined in order to determine the molecular geometry and symmetry.

Molecular Geometry of CCl4

Carbon tetrachloride has a tetrahedral molecular geometry. In a tetrahedral structure, the four chlorine atoms are symmetrically arranged around the central carbon atom at angles of about 109.5° from each other, providing a symmetric distribution of charge.

Symmetry and Dipole Moment

In a symmetrical tetrahedral molecule like CCl4, even though the bond between carbon and chlorine is polar, the symmetry causes the dipoles to cancel out each other. The dipoles from each C-Cl bond are equal and opposite, so they balance out to produce an overall dipole moment of zero.

Identify the Correct Answer

Given that CCl4 has a tetrahedral shape, making it symmetrical, the lack of a dipole moment is due to its symmetry in structure. Therefore, the correct answer is (b) its regular tetrahedral structure.

Key concepts

Carbon Tetrachloride

Carbon tetrachloride, commonly represented as CCl extsubscript{4}, is an organic compound composed of one carbon atom bonded to four chlorine atoms. This compound is known for being a colorless liquid at room temperature and being non-polar due to its unique structural properties. It is important to grasp the neutrality of this molecule when learning about dipole moments, as carbon tetrachloride is a classic example of molecular symmetry overcoming polar bonds to result in an overall non-polar molecule.
The bond between carbon and chlorine is polar because chlorine is more electronegative than carbon. However, in carbon tetrachloride, this potential for polarity is perfectly balanced by the symmetrical arrangement of the bonds in its three-dimensional structure, which we will discuss in more detail further on.

Molecular Geometry

The molecular geometry of a compound refers to the three-dimensional arrangement of atoms within a molecule. Understanding this concept is crucial in exploring how molecules interact, react, and form various structures.
For carbon tetrachloride, its molecular geometry takes the shape known as a tetrahedron. In this geometric configuration, each of the four chlorine atoms extends from the carbon atom to the vertices of an imaginary tetrahedron, resulting in bond angles of approximately 109.56. These angles are crucial in maintaining balance and symmetry, ensuring that the molecule remains neutral overall.

• Molecular geometry helps predict the chemical behavior of a molecule
• Symmetrical geometries usually indicate that dipole moments will cancel out
• A tetrahedral arrangement, as seen in CCl4, is one of the simplest symmetrical molecular shapes

Tetrahedral Structure

The tetrahedral structure is a type of molecular geometry where a central atom is located at the center of a tetrahedron, with other atoms positioned at the corners. In carbon tetrachloride, one carbon atom serves as the central atom, with four chlorine atoms equally spaced around it.
This even distribution stems from the tetrahedral coordination, causing all dipole moments in CCl extsubscript{4} to cancel out. Although carbon-chlorine bonds are polar, with chlorine pulling electrons more strongly, the tetrahedral symmetry ensures that these forces are balanced, which negates any overall dipole moment.
Understanding the tetrahedral structure clarifies why symmetrical molecules like carbon tetrachloride tend to be non-polar despite having polar bonds. This shape is foundational in molecular geometry studies, illustrating how structure influences molecular properties and behaviors.

• The tetrahedral shape results in even electronic distribution
• This structure allows for optimal molecule stability and reduced potential energy
• The perfect symmetry is why CCl extsubscript{4} lacks a dipole moment