Draw the Lewis structure for the following molecular formulas.
(l) SO₄^2-

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Step 1: Count the total number of valence electrons available for the molecule. Sulfur (S) belongs to Group 16 and has 6 valence electrons. Oxygen (O) also belongs to Group 16 and has 6 valence electrons each. Since the molecule has a charge of -2, add 2 extra electrons to the total count.

Step 2: Determine the central atom. Sulfur (S) is less electronegative than oxygen (O), so it will be the central atom. Arrange the four oxygen atoms around the sulfur atom.

Step 3: Connect the sulfur atom to each oxygen atom using single bonds. Each single bond represents 2 electrons. Subtract these electrons from the total valence electron count.

Step 4: Distribute the remaining electrons as lone pairs around the oxygen atoms to satisfy the octet rule for each oxygen. If there are leftover electrons, place them on the central sulfur atom.

Step 5: Check the formal charges on each atom. Adjust the bonding (e.g., by forming double bonds) if necessary to minimize formal charges while keeping the total charge of the molecule as -2.

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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 indicate bonds between atoms. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting reactivity.

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 structure and stability. For polyatomic ions like SO₄²⁻, calculating the total number of valence electrons is necessary for accurately constructing the Lewis structure.

Formal Charge

Formal charge is a concept used to determine the distribution of electrons in a molecule or ion. It is calculated by comparing the number of valence electrons in the free atom to the number of electrons assigned to it in the Lewis structure. Minimizing formal charges across a molecule helps identify the most stable structure, which is particularly important for polyatomic ions like sulfate (SO₄²⁻).

Draw the Lewis structure for the following molecular formulas. (l) SO42-