Question

How is the structure around a given atom related to repulsion between valence electron pairs on the atom?

Short answer

The structure around a given atom is related to the repulsion between valence electron pairs on the atom through the Valence Shell Electron Pair Repulsion (VSEPR) theory. This theory states that valence electron pairs will arrange themselves to minimize repulsion, resulting in specific electron pair geometries and molecular geometries. These geometries are a direct consequence of the repulsion between valence electrons and help ensure the molecule has an optimal and stable structure.

Step-by-step solution

Understand the Valence Shell Electron Pair Repulsion (VSEPR) Theory

In order to analyze the relationship between the structure of an atom and the repulsion between valence electron pairs, it is important to first understand the basics of the VSEPR theory. The theory states that electron pairs in the valence shell of a central atom will repel each other, and as a result, they will arrange themselves to minimize repulsion. This theory can help us predict the geometry of molecules and polyatomic ions.

Identifying the Central Atom

To use the VSEPR theory to predict the structure of a molecule, first identify the central atom in the molecule. The central atom is usually the least electronegative atom (except for hydrogen, which is never the central atom), or the atom with the highest number of connections to the other atoms.

Counting Valence Electrons

The next step in using the VSEPR theory is to count the total number of valence electrons for the molecule or polyatomic ion. This includes the electrons in the outermost shell of the central atom and the electrons shared by the bonding atoms. Valence electrons can be determined by looking at the group number of the element in the periodic table.

Determining Electron Pair Geometry

With the total number of valence electrons known, determine the electron pair geometry around the central atom. This geometry is dependent on the number of regions of high electron density (electron pair domains) surrounding the central atom. These electron pair domains include bonding pairs and lone pairs (nonbonding pairs) of electrons. The possible electron pair geometries include linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.

Determining Molecular Geometry

Once you have determined the electron pair geometry, use it to predict the molecular geometry by considering only the positions of the atoms (ignoring the lone pairs). The molecular geometry depends on the positions of the bonded atoms around the central atom, which are arranged to minimize repulsion between electron pairs. Examples of molecular geometries include linear, bent, trigonal planar, tetrahedral, and trigonal pyramidal.

Relating the Structure to Repulsion

Lastly, relate the molecular structure to the repulsion between valence electron pairs. According to VSEPR theory, the structure around a given atom is a direct result of the repulsion between valence electron pairs on the atom, as they try to minimize repulsion in order to achieve the most stable configuration. This ensures that the molecule has an optimal structure, given the repulsion between its valence electrons. In conclusion, the structure around a given atom is related to the repulsion between valence electron pairs on the atom, as described by the VSEPR theory. The electron pairs arrange themselves in a way that minimizes repulsion, leading to predictable molecular geometries that allow for the most stable molecular configuration.