Question

Consider a hypothetical simple ion \(\mathrm{M}^{2+}\). Determine the formula of the compound this ion would form with each of the following anions. a. acetate b. permanganate c. oxide d. hydrogen phosphate e. hydroxide f. nitrite

Short answer

a. M(C₂H₃O₂)₂ b. M(MnO₄)₂ c. MO d. MHPO₄ e. M(OH)₂ f. M(NO₂)₂

Step-by-step solution

1. Anion Charges

To predict the formula of the compound that will form between M^2+ and each of the given anions, we first need to determine the charge of these anions: a. Acetate: C₂H₃O₂⁻ - Charge: -1 b. Permanganate: MnO₄⁻ - Charge: -1 c. Oxide: O²⁻ - Charge: -2 d. Hydrogen phosphate: HPO₄²⁻ - Charge: -2 e. Hydroxide: OH⁻ - Charge: -1 f. Nitrite: NO₂⁻ - Charge: -1

2. Determining the Compounds

Now that we have the charges of the anions, let's combine them with the M^2+ ion in such a way that the total charge of the compound is neutral. a. M^2+ + C₂H₃O₂⁻: Since the charge on M^2+ is +2 and on acetate is -1, we need two acetate ions to balance the charges. Compound: M(C₂H₃O₂)₂ b. M^2+ + MnO₄⁻: The charge on M^2+ is +2 and on permanganate is -1, so we need two permanganate ions to balance the charges. Compound: M(MnO₄)₂ c. M^2+ + O²⁻: Since the charge on M^2+ is +2, and on oxide is -2, only one oxide ion is needed to balance the charge. Compound: MO d. M^2+ + HPO₄²⁻: The charge on M^2+ is +2 and on hydrogen phosphate is -2, only one hydrogen phosphate ion is needed to balance the charge. Compound: MHPO₄ e. M^2+ + OH⁻: Since the charge on M^2+ is +2 and on hydroxide is -1, we need two hydroxide ions to balance the charges. Compound: M(OH)₂ f. M^2+ + NO₂⁻: The charge on M^2+ is +2 and on nitrite is -1, so we need two nitrite ions to balance the charges. Compound: M(NO₂)₂ In summary, the hypothetical simple ion M^2+ forms the following compounds when combined with the given anions: a. M(C₂H₃O₂)₂ b. M(MnO₄)₂ c. MO d. MHPO₄ e. M(OH)₂ f. M(NO₂)₂

Key concepts

Ions and Charges

To understand chemical compound formulation with ions, it’s essential to know about the charges that ions possess. An ion is an atom or molecule that has lost or gained one or more electrons, hence acquiring an electric charge. We have two main types of ions: cations and anions.

• Cations are positively charged ions. They form when an atom loses one or more electrons, resulting in more protons than electrons. In our exercise, a hypothetical ion like \( \text{M}^{2+} \) is a cation with a +2 charge.
• Anions are negatively charged ions. These are formed when an atom gains electrons, causing it to have more electrons than protons. For instance, acetate (C₂H₃O₂⁻) and oxide (O²⁻) are anions with charges of -1 and -2 respectively in this context.

Knowing the charges of ions is crucial as it determines how they will combine to form compounds, thereby guiding us toward achieving chemical neutrality in compounds.

Anion-Cation Combination

When cations and anions combine to form compounds, they do so in a way that neutralizes the total charge. This means the sums of the positive and negative charges must equal zero. This process is often referred to as anion-cation combination.

In our problem, we have a \( \text{M}^{2+} \) ion. We aim to form compounds using this ion and various anions. Each anion has a defined charge, and we must balance these charges with the \( \text{M}^{2+} \) ion.

• If an anion like acetate has a charge of -1, as with \( \text{C}_{2} \text{H}_{3} \text{O}_{2}^{-} \), you need two of them to balance one \( \text{M}^{2+} \) ion, forming the compound \( \text{M(C}_{2} \text{H}_{3} \text{O}_{2})_{2} \).
• An anion with a -2 charge, like oxide (\( \text{O}^{2-} \)), only requires one to combine with \( \text{M}^{2+} \), resulting in \( \text{MO} \).

Balancing these charges correctly is vital for arriving at the right compound formula, and each combination must result in a neutral compound.

Chemical Neutrality

Achieving chemical neutrality is a fundamental goal in forming compounds. For a compound to be stable and neutral, the total positive charge from the cations must exactly cancel out the total negative charge from the anions. This neutrality ensures that the compound does not have an overall charge, which is essential for its stability.

Consider the formation of a compound between \( \text{M}^{2+} \) and nitrite (\( \text{NO}_{2}^{-} \)). The \( \text{M}^{2+} \) ion has a +2 charge, while the nitrite ion has a -1 charge. To achieve a neutral compound, you would need two nitrite ions for every \( \text{M}^{2+} \) ion, forming \( \text{M(NO}_{2})_{2} \).

In summary, when forming compounds, ensure that:

• The number of positive and negative charges in the compound are equal.
• The final formulation results in a compound with no net charge.

This need for chemical neutrality is the guiding principle behind combining ions into stable compounds, making it a core concept in chemistry.