Question

How are the hydrogen atoms arranged in space in methane, \(\mathrm{CH}_{4} ?\)

Short answer

In methane \(\text{CH}_4\), the hydrogen atoms are arranged tetrahedrally around the carbon atom with \(\text{109.5}^{\text{°}}\) bond angles.

Step-by-step solution

- Understand the Molecular Structure of Methane

Methane, with the chemical formula \(\text{CH}_4\), consists of one carbon atom surrounded by four hydrogen atoms. Carbon has four valence electrons and needs four more electrons to complete its octet.

- Recognize the Shape of Methane

Due to the four pairs of bonding electrons, the molecular geometry of methane is tetrahedral. This minimizes the repulsion between the electron pairs.

- Describe the Tetrahedral Structure

In a tetrahedral structure, the hydrogen atoms are positioned at the four vertices of a tetrahedron, with the carbon atom at the center. The bond angles between the hydrogen atoms are \(\text{109.5}^{\text{°}}\).

- Visualize the Spatial Arrangement

Each hydrogen atom is spaced equally around the central carbon atom, creating a three-dimensional shape. This equidistant arrangement ensures maximum separation and minimizes repulsion.

Key concepts

Methane Structure

Methane is a simple molecule with the chemical formula \(\text{CH}_4\). It consists of one carbon atom bonded to four hydrogen atoms.
The carbon atom has four valence electrons and needs four more to complete its outer shell.
Since each hydrogen atom has one electron, it shares its electron with carbon, forming a covalent bond.
In methane, there are four such covalent bonds, creating a stable molecule.

Tetrahedral Geometry

The molecular geometry of methane is characterized as tetrahedral.
This is due to the arrangement of four pairs of bonding electrons around the central carbon atom.
In a tetrahedral structure, the electron pairs are arranged as far apart as possible to minimize repulsion.
This results in a three-dimensional shape where the hydrogen atoms are at the corners of a tetrahedron, and the carbon is at the center. Visualizing this structure can be easier if you imagine a triangular pyramid with a hydrogen atom at each vertex.

Bond Angles

In the tetrahedral geometry of methane, the bond angles between the hydrogen atoms are \(\text{109.5}^{\text{°}}\).
These angles are a result of the equal repulsion between the electron pairs.
This specific angle helps in maintaining the three-dimensional structure of methane.
If the angles were any different, the stability and shape of the molecule would be compromised.

Electron Pair Repulsion

The concept of electron pair repulsion is key to understanding the shape of methane.
According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, electron pairs repel each other.
This repulsion forces them to stay as far apart as possible, which determines the geometry of the molecule.
In methane, the four pairs of bonding electrons try to maximize their distance apart, resulting in the tetrahedral shape.
This ensures that repulsion is minimized and the molecule remains stable.