Determine the name of the third compound. The third compound is Cd3P2. Cadmium (Cd) is capable of forming more than one cation, so the charge of the anion must be calculated first. The charge of the phosphide anion (P3-) is (-3). Cd3P2 contains 2 phosphorus atoms, therefore the total negative charge is 2(-3), or (-6). The subscript of the cadmium atom is 3, so a charge of (+2) is required to balance the (-6) charge: total positive charge + total negative charge = 3(+2) + 2(-3). The name of the compound Cd3P2 is cadmium phosphide. Calculate the number of anions that will bond with a given cation to form a neutral species. Calculate the number of cations that will bond with a given anion to form a neutral species. Calculate the number of atoms of a given element in one formula unit of a compound. Identify the number and types of ions present in an ionic compound.
The Correct Answer and Explanation is:
Correct Answer:
The name of the compound Cd₃P₂ is cadmium phosphide.
Explanation:
Cd₃P₂ is an ionic compound composed of cadmium (Cd) and phosphorus (P). To determine its name, charge balance, and the number of ions involved, we must first understand the charges of the individual ions:
- Phosphorus (P) typically forms the phosphide ion, which has a charge of –3 (written as P³⁻).
- Cadmium (Cd) commonly forms a +2 cation (written as Cd²⁺). Although many transition metals form multiple cations, cadmium only forms Cd²⁺ in most of its compounds.
Now, in the compound Cd₃P₂:
- There are 2 phosphorus atoms, each with a –3 charge, giving a total negative charge of –6.
- There are 3 cadmium atoms, each with a +2 charge, giving a total positive charge of +6.
When the total positive charge (+6) and the total negative charge (–6) are added, the result is zero. This confirms that Cd₃P₂ is a neutral compound, and the charges are properly balanced.
Thus, the chemical formula tells us:
- 3 Cd²⁺ cations
- 2 P³⁻ anions
This ratio gives the compound Cd₃P₂, and the correct name is cadmium phosphide.
To summarize additional points:
- Number of anions that bond with a given cation: For Cd²⁺ and P³⁻ to balance, 3 Cd²⁺ ions bond with 2 P³⁻ ions.
- Number of atoms in one formula unit: 3 cadmium atoms, 2 phosphorus atoms.
- Types of ions: 3 Cd²⁺ cations and 2 P³⁻ anions.
- Compound type: Ionic compound.
