Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. PF₅

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Identify the total number of valence electrons in the molecule. Phosphorus (P) has 5 valence electrons, and each fluorine (F) has 7 valence electrons. Since there are 5 fluorine atoms, calculate the total number of valence electrons.

Determine the central atom. In PF5, phosphorus is the central atom because it is less electronegative than fluorine and can form more bonds.

Draw a skeletal structure with phosphorus in the center and single bonds connecting it to each of the five fluorine atoms.

Distribute the remaining valence electrons to satisfy the octet rule for each fluorine atom. Each fluorine should have 8 electrons around it, including the bonding pair.

Check if the central atom (phosphorus) can have an expanded octet. Phosphorus can have more than 8 electrons, so ensure all valence electrons are used and the structure is stable.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds between atoms. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting the behavior of molecules.

Expanded Octet

An expanded octet refers to the ability of certain elements, particularly those in the third period and beyond, to accommodate more than eight electrons in their valence shell. This occurs because these elements have d orbitals available for bonding. In the case of PF5, phosphorus can form five bonds, thus exceeding the octet rule.

Molecular Geometry

Molecular geometry describes the three-dimensional arrangement of atoms within a molecule. It is influenced by the number of bonding pairs and lone pairs of electrons around the central atom, which can affect the molecule's shape and reactivity. For PF5, the geometry is trigonal bipyramidal, which is crucial for understanding its chemical properties and interactions.

Write Lewis structures for each molecule or ion. Use expanded octets as necessary. a. PF5