Problem 42 - Chemistry The Molecular Science

Question

Write the chemical formulas for these compounds. (a) Nickel(II) nitrate (b) Sodium bicarbonate (c) Lithium hypochlorite (d) Magnesium chlorate (e) Calcium sulfite

Step-by-Step Solution

Answer

(a) Ni(NO₃)₂, (b) NaHCO₃, (c) LiClO, (d) Mg(ClO₃)₂, (e) CaSO₃.

Step 1: Understand Compound Information

Let's start each compound one by one: 1. Nickel(II) nitrate means nickel with a +2 oxidation state, combined with nitrate ions. 2. Sodium bicarbonate includes sodium ions (Na) and bicarbonate ions. 3. Lithium hypochlorite is lithium ions (Li) combined with hypochlorite ions. 4. Magnesium chlorate includes magnesium ions (Mg) and chlorate ions. 5. Calcium sulfite is made of calcium ions (Ca) and sulfite ions.

Step 2: Identify Ions and Charges

For each compound: 1. Nickel(II) ion: Ni^{2+}, Nitrate ion: NO_3^{-}. 2. Sodium ion: Na^{+}, Bicarbonate ion: HCO_3^{-}. 3. Lithium ion: Li^{+}, Hypochlorite ion: ClO^{-}. 4. Magnesium ion: Mg^{2+}, Chlorate ion: ClO_3^{-}. 5. Calcium ion: Ca^{2+}, Sulfite ion: SO_3^{2-}.

Step 3: Write Formulas by Balancing Charges

Write the chemical formulas by combining ions so that charges are balanced:1. Nickel(II) nitrate: Combine Ni^{2+} and two NO_3^{-} ions to balance the charge: \(\text{Ni(NO}_3\text{)}_2\).2. Sodium bicarbonate: Combine Na^{+} and HCO_3^{-} ions: \(\text{NaHCO}_3\).3. Lithium hypochlorite: Combine Li^{+} and ClO^{-} ions: \(\text{LiClO}\).4. Magnesium chlorate: Combine Mg^{2+} and two ClO_3^{-} ions to balance the charge: \(\text{Mg(ClO}_3\text{)}_2\).5. Calcium sulfite: Combine Ca^{2+} and one SO_3^{2-} ion: \(\text{CaSO}_3\).

Key Concepts

Ionic Compounds

Ionic compounds are made up of positive and negative ions that are held together by electrostatic forces. These compounds usually form between metals and non-metals. The metal loses electrons to become a positively charged ion, also known as a cation. The non-metal gains electrons to become a negatively charged ion, known as an anion.

The overall charge of an ionic compound must be zero, meaning the total positive charge must equal the total negative charge. This balance is crucial for forming stable compounds. Understanding ionic compounds is essential when learning to write chemical formulas, as it helps predict how atoms and ions will combine.

Oxidation State

Oxidation state, or oxidation number, is a way of determining the degree of oxidation or electron control a particular element or ion has within a compound. It is expressed as a charge and helps in understanding how electrons are distributed in a molecule.

In Nickel(II) nitrate, "Ni" has an oxidation state of +2, as indicated by the Roman numeral II. This information guides us to know that nickel will lose two electrons, suggesting how it interacts with other ions like nitrate, which has a -1 charge for each ion. Recognizing oxidation states is crucial for grasping ionic interactions and writing balanced chemical equations.

• Positive oxidation state: means losing electrons (e.g., Ni²⁺).
• Negative oxidation state: means gaining electrons (e.g., NO₃^-).

Balancing Charges

Balancing charges in a chemical formula is essential to ensure that the total positive charges equal the total negative charges in the compound. This ensures that the compound is neutral overall.

For instance, in Nickel(II) nitrate, nickel has a +2 charge. To balance the charges, two nitrate ions, each with a -1 charge, are needed. This results in the formula \(\text{Ni(NO}_3\text{)}_2\).

The approach is applicable to all ionic compounds:

• Identify the charges of the ions involved.
• Determine the number of each ion needed to balance the charges.
• Write the chemical formula ensuring the total charge is zero.

Mastering balancing charges helps in writing correct formulas and understanding the structure of compounds.

Polyatomic Ions

Polyatomic ions are groups of atoms that behave as a single charged entity. They play a crucial role in forming various ionic compounds. Unlike monatomic ions, which consist of a single atom, polyatomic ions consist of two or more atoms covalently bonded together, but they have an overall charge.

Some common polyatomic ions include:

• Nitrate (NO₃^-)
• Bicarbonate (HCO₃^-)
• Chlorate (ClO₃^-)
• Sulfite (SO₃^2-)

When writing chemical formulas, it's important to recognize these ions and correctly apply their charges. For example, the nitrate ion is used in balancing the charge of nickel in the compound nickel(II) nitrate. Understanding these polyatomic ions makes it easier to predict the formula of compounds containing them.