What is the formula of the ionic compound rubidium cyanide
The Correct Answer and Explanation is:
The formula for the ionic compound rubidium cyanide is RbCN.
To determine the chemical formula for an ionic compound, a systematic approach involving the identification of its constituent ions and their respective charges is necessary.
First, the cation, which is the positively charged ion, must be identified. In “rubidium cyanide,” the cation is derived from the element rubidium (Rb). Rubidium is an alkali metal located in Group 1 of the periodic table. Elements in this group characteristically lose their single valence electron to achieve a stable electron configuration, similar to that of a noble gas. By losing one electron, a rubidium atom forms a cation with a charge of +1. The symbol for the rubidium ion is therefore Rb⁺.
Second, the anion, the negatively charged ion, is identified. The name “cyanide” indicates that this is a polyatomic ion, meaning it is composed of multiple atoms covalently bonded together that carry an overall net charge. The cyanide ion consists of one carbon atom and one nitrogen atom. It has a well-established formula and charge of CN⁻. This -1 charge arises from the overall electron distribution within the bonded atoms.
Finally, the ions are combined to form an electrically neutral compound. The fundamental principle of forming an ionic compound is that the total positive charge from the cations must exactly balance the total negative charge from the anions. In this case, the rubidium ion (Rb⁺) has a charge of +1, and the cyanide ion (CN⁻) has a charge of -1. A single rubidium ion provides a +1 charge, which perfectly balances the -1 charge of a single cyanide ion.
This means the ions combine in a simple one-to-one ratio. When writing the final formula, the symbol for the cation (Rb) is written first, followed by the symbol for the anion (CN). Since the ratio is 1:1, no subscripts are needed. The resulting formula is RbCN.
