Question

Predict which of the following polyatomic anions has an ionic charge of 2 -. (Hint: The total number of valence electrons must be an even number.) (a) periodate ion, \(\mathrm{IO}_{4}^{2-}\) (b) silicate ion, \(\mathrm{SiO}_{3}^{2-}\)

Short answer

Silicate ion \(\text{SiO}_{3}^{2-}\) has an ionic charge of \(2-\).

Step-by-step solution

Understand the given ions

Examine the given polyatomic anions: - Periodate ion: \( \text{IO}_{4}^{2-} \)- Silicate ion: \( \text{SiO}_{3}^{2-} \)You are tasked to determine which has a total ionic charge of \(2-\) based on their valence electrons being an even number.

Calculate valence electrons for the periodate ion

For \( \text{IO}_{4}^{2-} \):- Iodine (I) is in Group 17, so it has 7 valence electrons.- Oxygen (O) is in Group 16, and each has 6 valence electrons.Total valence electrons: \[7 + 4 \times 6 + 2 = 33 \text{ (from the ion charge)}\]The valence electrons count is odd, which is incorrect.

Calculate valence electrons for the silicate ion

For \( \text{SiO}_{3}^{2-} \):- Silicon (Si) is in Group 14, so it has 4 valence electrons.- Oxygen (O) is in Group 16, with each having 6 valence electrons.Total valence electrons: \[4 + 3 \times 6 + 2 = 24 \text{ (from the ion charge)}\]The total is even, satisfying the condition given in the hint.

Make your prediction

Based on the calculations, the silicate ion \(\text{SiO}_{3}^{2-}\) has an even number of total valence electrons, aligning with the criterion given for the ionic charge of \(2-\).

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding. They determine how atoms interact and bond with each other. As the exercise demonstrated, different atoms have varying numbers of valence electrons depending on their group in the periodic table.

• Iodine, in Group 17, has 7 valence electrons.
• Oxygen, from Group 16, has 6 valence electrons each.
• Silicon, belonging to Group 14, contains 4 valence electrons.

Valence electrons are essential in forming polyatomic ions like the periodate and silicate ions, as they help decide the molecule's valence shell electron pair repulsion (VSEPR) shape, influence reactivity, and determine the possibility for ionic equilibrium. Understanding the number of valence electrons allows chemists to predict molecular structure and bonding.

Ionic Charge

Ionic charge is the net charge of an ion that results from the atom either losing or gaining electrons to fulfill an octet in its outer shell. In polyatomic ions like periodate and silicate, the ionic charge arises from the total valence electrons present.

• An even number of valence electrons will mean the ion is more likely to have a stable structure.
• Ionic charges are vital for determining an ion's chemical behavior.

In the original exercise, the silicate ion was verified to have an ionic charge of \(2-\). This was concluded by verifying that the total number of valence electrons was even, fulfilling the exercise's condition. The charge affects how ions interact and combine with other ions, forming various compounds and shapes.

Silicate Ion

The silicate ion, \(\text{SiO}_3^{2-}\), is a complex polyatomic anion made up of silicon and oxygen atoms. Understanding its structure is essential for grasping its role in chemistry.The silicate ion contains:

• One silicon atom contributing 4 valence electrons.
• Three oxygen atoms each offering 6 valence electrons.
• An extra 2 electrons from the \(2-\) charge.

In total, this results in 24 valence electrons, a crucial factor leading to its stable structure.Silicate ions are found in various minerals and materials, forming the backbone of rocks and soils. Their tetrahedral shape connects through oxygen atoms, creating three-dimensional structures that are vital for many geological processes. Recognizing how the silicate ion fits within larger structures helps appreciate its significance in both natural and synthetic materials.

Chemical Bonding

Chemical bonding is the interaction that holds atoms together in compounds. There are several types of chemical bonds, including ionic, covalent, and metallic bonds. In the context of polyatomic ions:

• Valence electrons are shared or transferred among atoms to create bonds.
• Ionic charge influences the overall bonding nature and stability of the ions.

The silicate ion exhibits covalent bonding between silicon and oxygen atoms, while extra electrons balance the ionic charge, helping to stabilize the entire ion. Chemical bonding defines the physical and chemical properties of substances, illustrating why certain molecules behave predictably under varying conditions. Sound knowledge of chemical bonding principles allows students to better predict reactions and understand molecular interactions, vital skills in any chemistry-related field.