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Writing Formula Units of Ionic Compounds quiz #1 Flashcards

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Writing Formula Units of Ionic Compounds quiz #1
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  • Can a stable compound be formed from lithium and oxygen? If so, what is its formula unit?
    Yes, a stable ionic compound can be formed from lithium and oxygen. Lithium forms Li+ ions and oxygen forms O2- ions. Using the crisscross method, the formula unit is Li2O.
  • What is the formula unit of the compound formed when zinc reacts with sulfur?
    When zinc reacts with sulfur, zinc forms Zn2+ ions and sulfur forms S2- ions. Since the charges are equal and opposite, they cancel out, and the formula unit is ZnS.
  • What ions make up the compound FeCl3?
    FeCl3 is made up of Fe3+ (iron(III) ion) and Cl- (chloride ion).
  • In the compound aluminum oxide, which element acts as the cation?
    In aluminum oxide, aluminum (Al) acts as the cation (Al3+), and oxygen (O2-) is the anion.
  • Which type of element can replace X in the formula Mg3X2 to form a stable ionic compound?
    In Mg3X2, magnesium forms Mg2+ ions. To balance the charges, X must be an element that forms a 3- anion, such as a group 5A element like nitrogen (N3-).
  • What does the formula unit of an ionic compound represent in terms of its structure?
    The formula unit represents the simplest ratio of ions that combine to give a neutral charge in an ionic solid. It does not reflect the full crystal lattice structure, which is a 3D arrangement of many ions.
  • How does the crystal lattice of an ionic compound differ from an ionic pair?
    A crystal lattice is a 3D arrangement of many cations and anions forming a stable pattern. An ionic pair refers only to a single positive ion and a single negative ion, which is not the true structure of an ionic solid.
  • What is the first step in writing the formula for an ionic compound from its name?
    The first step is to write the ions involved in the compound based on the provided name. This involves determining the charges of the cation and anion using the periodic table or known polyatomic ions.
  • When crisscrossing to write ionic compound formulas, what part of the ion notation is crisscrossed?
    Only the numbers from the charges are crisscrossed, not the charge signs themselves. This ensures the resulting formula is electrically neutral.
  • Why are parentheses used in the formula for barium phosphate?
    Parentheses are used to indicate that the subscript applies to the entire polyatomic ion, not just one element. In Ba3(PO4)2, the '2' applies to both phosphorus and oxygen in the phosphate ion.