Problem 37 - Chemistry and Chemical Reactivity

Question

Give the symbol, including the correct charge, for each of the following ions: (a) barium ion (b) titanium(IV) ion (c) phosphate ion (d) hydrogen carbonate ion (e) sulfide ion (f) perchlorate ion (g) cobalt(II) ion (h) sulfate ion

Step-by-Step Solution

Answer

(a) \( \text{Ba}^{2+} \), (b) \( \text{Ti}^{4+} \), (c) \( \text{PO}_4^{3-} \), (d) \( \text{HCO}_3^{-} \), (e) \( \text{S}^{2-} \), (f) \( \text{ClO}_4^{-} \), (g) \( \text{Co}^{2+} \), (h) \( \text{SO}_4^{2-} \).

Step 1: Find the Barium Ion Symbol

Barium is an alkaline earth metal in group 2 of the periodic table, which means it typically forms a 2+ charge when it becomes an ion. Therefore, the ion symbol is \( \text{Ba}^{2+} \).

Step 2: Determine the Titanium(IV) Ion Symbol

Titanium(IV) indicates titanium has a +4 charge. Therefore, the symbol for the titanium(IV) ion is \( \text{Ti}^{4+} \).

Step 3: Identify the Phosphate Ion Symbol

Phosphate is a polyatomic ion with the formula \( \text{PO}_4^{3-} \) indicating a 3- charge.

Step 4: Write the Hydrogen Carbonate Ion Symbol

The hydrogen carbonate ion, also known as bicarbonate, has the formula \( \text{HCO}_3^{-} \).

Step 5: Find the Sulfide Ion Symbol

Sulfide is an ion formed by sulfur, typically with a 2- charge, and its symbol is \( \text{S}^{2-} \).

Step 6: Determine the Perchlorate Ion Symbol

Perchlorate is a polyatomic ion with a 1- charge and the formula \( \text{ClO}_4^{-} \).

Step 7: Write the Cobalt(II) Ion Symbol

Cobalt(II) indicates cobalt has a +2 charge. Therefore, the symbol for the cobalt(II) ion is \( \text{Co}^{2+} \).

Step 8: Identify the Sulfate Ion Symbol

Sulfate is a polyatomic ion with the formula \( \text{SO}_4^{2-} \) indicating a 2- charge.

Key Concepts

Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded that function as a single charged entity. They are quite important in chemistry because many compounds involve these groups. Typically, a polyatomic ion will have a specific name and formula. For instance, the phosphate ion, with the formula \( \text{PO}_4^{3-} \), carries a 3- charge.
Another common polyatomic ion is sulfate, represented as \( \text{SO}_4^{2-} \), which has a 2- charge.
Polyatomic ions often participate in forming salts and other compounds by combining with opposite charges. Some examples include:

• Phosphate \( \text{PO}_4^{3-} \)
• Hydrogen carbonate \( \text{HCO}_3^{-} \), also called bicarbonate
• Perchlorate \( \text{ClO}_4^{-} \)

These ions are commonly found in everyday substances, including fertilizers and cleaning agents, making understanding them crucial.

Charge of Ions

Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a net charge. Whether an atom becomes an anion (negatively charged) or a cation (positively charged) depends on its electron configuration and its tendency to lose or gain electrons to achieve a stable electron shell.
For example, titanium(IV) means titanium loses four electrons, leading to a charge of \( 4+ \), as seen in \( \text{Ti}^{4+} \). Meanwhile, a sulfide ion has gained two electrons, resulting in a \( 2- \) charge as \( \text{S}^{2-} \).
Understanding ion charges is crucial because they dictate the ratios in which ions combine to form neutral compounds. Ions follow specific rules:

• Metals typically lose electrons to form positive ions or cations.
• Nonmetals typically gain electrons to form negative ions or anions.
• Ions combine in ratios that neutralize the overall charge.

These principles help predict chemical formulas and reactions, providing critical insight into how substances combine and interact.

Alkaline Earth Metals

Alkaline earth metals are found in Group 2 of the periodic table. They are characterized by their shiny appearance and high reactivity, especially with water.
Common alkaline earth metals include barium, magnesium, and calcium. These elements always tend to lose two electrons to achieve a stable electronic configuration, resulting in a \( 2+ \) charge. For example, the barium ion is written as \( \text{Ba}^{2+} \), reflecting its typical charge after losing two electrons.
Key properties of alkaline earth metals:

• They have two electrons in their outer shell.
• They form cations with a \( 2+ \) charge in reactions.
• They are typically denser and harder than alkali metals.

Understanding these elements aids in predicting their reactivity and the types of compounds they may form, making them pivotal in areas such as biochemical pathways and industrial applications.

Transition Metal Ions

Transition metals are unique elements found in the central block of the periodic table, specifically in groups 3-12. These metals are known for their ability to form cations with varying charges, unlike the predictable charges of alkaline earth metals. For instance, cobalt can form ions such as cobalt(II) \( \text{Co}^{2+} \) or cobalt(III) depending on how many electrons are lost. Titanium is another example, where the charge may vary, as seen in titanium(IV) \( \text{Ti}^{4+} \).
Important characteristics of transition metals include:

• They can form various ionic charges.
• They often form colored compounds.
• They are good conductors of heat and electricity.

Due to their varied oxidation states, transition metals are widely used in industrial catalysts and electronic applications. Understanding their versatile chemistry is essential for students studying chemistry, material science, or engineering.