Write the Lewis structure for each molecule. a. PH₃ b. SCl₂ c. HI

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Determine the total number of valence electrons in the molecule. Phosphorus (P) has 5 valence electrons, and each hydrogen (H) has 1 valence electron. Since there are three hydrogen atoms, the total number of valence electrons is 5 + 3(1) = 8.

Place the least electronegative atom in the center. In PH_3, phosphorus is less electronegative than hydrogen, so phosphorus will be the central atom.

Connect each hydrogen atom to the central phosphorus atom with a single bond. Each P-H bond will use 2 valence electrons, so 3 bonds will use 6 electrons.

Distribute the remaining valence electrons to satisfy the octet rule for the central atom. After forming the bonds, 2 electrons remain, which will be placed as a lone pair on the phosphorus atom.

Verify that all atoms have a complete valence shell. Hydrogen atoms are satisfied with 2 electrons each, and phosphorus has 8 electrons around it (6 from bonds and 2 from the lone pair).

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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.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in determining how atoms bond with each other. The number of valence electrons influences the molecule's reactivity and stability. For example, phosphorus (P) has five valence electrons, which play a key role in forming bonds in molecules like PH3.

Molecular Geometry

Molecular geometry refers to 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. In the case of PH3, the geometry is trigonal pyramidal due to the presence of one lone pair on phosphorus, affecting the molecule's shape and properties.

Write the Lewis structure for each molecule. a. PH3 b. SCl2 c. HI