Consider the Lewis structure for the polyatomic oxyanion shown here, where X is an element from the third period (Na - Ar). By changing the overall charge, n, from 1- to 2- to 3- we get three different polyatomic ions. For each of these ions (b) determine the formal charge of the central atom, X;

Verified step by step guidance

1. Step 1: Identify the central atom X and its possible oxidation states. Since X is from the third period, it could be any element from Na to Ar.
2. Step 2: Write the general formula for the polyatomic oxyanion, considering the central atom X and the surrounding oxygen atoms.
3. Step 3: Use the formula for formal charge: \( \text{Formal Charge} = \text{Valence Electrons} - \text{Non-bonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons} \).
4. Step 4: Calculate the formal charge of the central atom X for each ion with charges 1-, 2-, and 3-. Adjust the number of electrons accordingly for each charge.
5. Step 5: Compare the formal charges for each ion to understand how the change in overall charge affects the formal charge of the central atom X.

Key Concepts

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 help visualize the arrangement of electrons and the connectivity of atoms, which is crucial for understanding molecular geometry and reactivity. In the context of polyatomic ions, Lewis structures also illustrate how charges are distributed among atoms.

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated based on the number of valence electrons, the number of non-bonding electrons, and half the number of bonding electrons. It helps in determining the most stable structure of a molecule or ion by minimizing the formal charges across the atoms. Understanding formal charge is essential for evaluating the stability and reactivity of different polyatomic ions.

Polyatomic Ions

Polyatomic ions are charged species composed of two or more atoms covalently bonded together, which can carry an overall positive or negative charge. The charge arises from the loss or gain of electrons, and different charges can lead to the formation of various ions from the same central atom. Recognizing how the charge affects the Lewis structure and formal charge is key to analyzing the properties of these ions.