Binary lonic Compounds, TYPE I Type I ionic compounds refer to compounds made from metal ions that always have the same charge. For example, the potassium always forms an ion with a +1 charge. Example Formulas and Names: KI = potassium iodide Ag
N = silver nitride ZnF
= zinc fluoride Na
S = sodium sulfide STOP Watch “Binary lonic Compounds Tutorial” video on Canvas, then continue a. Which type of element (metal or nonmetal) is always listed first in the name? b. What is the common ending for all names? c. Consider the compound CaF
: i. What is the charge on the calcium? ii. What is the charge on each of the fluorine ions? iii. Why does the compound need 2 fluorine ions? iv. Is the name of this compound calcium difluoride? Why or why not?
The Correct Answer and Explanation is:
Answers:
a. The metal is always listed first in the name of a binary ionic compound.
b. The common ending for all names is “-ide”.
c. CaF₂ Analysis:
i. The charge on the calcium ion is +2.
ii. The charge on each fluorine ion is -1.
iii. The compound needs 2 fluorine ions to balance the +2 charge of one calcium ion. Two fluorides at -1 each provide a total of -2, which balances the +2 charge of calcium.
iv. The name is not calcium difluoride. The correct name is calcium fluoride because in Type I binary ionic compounds, prefixes like “di” are not used in the naming.
Explanation
Binary ionic compounds of Type I consist of two elements — a metal cation with a fixed positive charge and a nonmetal anion. These metals typically belong to Groups 1, 2, and a few others like silver (Ag⁺), zinc (Zn²⁺), and aluminum (Al³⁺), which always form ions with the same charge.
In naming these compounds, the metal is always written and named first, followed by the nonmetal, which takes the suffix “-ide”. This format ensures clarity, especially since no Roman numerals or prefixes are needed for fixed-charge metals.
Take calcium fluoride (CaF₂) as an example. Calcium, a Group 2 metal, forms a consistent +2 charge. Fluorine, a halogen, forms a -1 charge. To achieve electrical neutrality in the compound, one calcium ion (+2) must pair with two fluoride ions (each -1) to yield a net charge of zero: +2 + (-1) + (-1) = 0.
The name “calcium fluoride” reflects this composition. Even though there are two fluorine atoms, prefixes like “di-” are not used in binary ionic naming rules for Type I compounds. Prefixes such as mono-, di-, or tri- are only used in molecular compounds (usually nonmetal + nonmetal).
In summary, understanding the charges and naming rules is essential in constructing and identifying correct chemical formulas and names for binary ionic compounds. This consistent system helps chemists communicate precisely about chemical substances.
