Ionic Formulas and Names Topic 14 Ionic Compounds
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Ionic Formulas and Names Topic #14
Ionic Compounds • Chemical Formula- tells you how many cations and anions exist in a compound. • Binary Compounds- compounds consisting of 2 elements • Ternary Compounds- compounds consisting of three different elements.
Writing Ionic Formulas: Rules Rule 1 The positive ion is placed first in the formula, the negative ion is second. • For example, KF, Ca. O
Rule 2 Positive and negative ions are combined so that the total number of positive charges is balanced by the total number of negative charges. • For example, Ca. S, Ca. Cl 2, Al. Cl 3 and Al 2 O 3
• Rule 3 When there are two or more of a particular ion in a compound, then in the chemical formula the number is written as a subscript after the chemical symbol. For example, Al 2 O 3 • IMPORTANT when writing formulas, never write charges, although the ions still have a charge because that’s what keeps them bonded.
Charges of Representative Elements Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 6
Ionic Naming Compound Names generally consist of two words. For ionic compounds, name the cation first then the anion. Remember the anion should end in –ide. Compound Formula Ca. Cl 2 Na. Br Al 2 S 3 Name Calcium Chloride Sodium Bromide Aluminum Sulfide Note: Notice how it does not matter the number of ions, the name simply states the cation and the anion
