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Binary Ionic Compounds. Naming and Writing formulas. Ionic Compounds:. Formed by combining a cation with an anion . Held together by an ionic bond The attractive force between ions of opposite charge. Crystal lattice structure: Repeating ordered pattern of positive and negative ions
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Binary Ionic Compounds Naming and Writing formulas
Ionic Compounds: • Formed by combining a cationwith an anion. • Held together by an ionic bond • The attractive force between ions of opposite charge. • Crystal lattice structure: • Repeating ordered pattern of positive and negative ions • Represented by a formula unit • Displays the lowest ratio of ions in the crystal • Example: CaCl2
Forming Cations and anions • Cation: Positively charged ion formed by an atom losing one or more electrons; usually a metal • Example: calcium loses two electron. • Anion: Negatively charged ion formed by an atom gaining one or more electrons; usually a nonmetal. • Example: chlorine gains one electron.
Learning Check: • Determine the number of electrons either lost or gained when forming the following ions: • S-2 • Na+1 • Al+3 • Br-1 • N-3 • Are the ions listed above cations or anions? • 1. • 2. • 3. • 4. • 5.
Naming Binary ionic compounds • Binary = 2 elements (metal w/ one nonmetal) • Step #1: • Name the cation first. • Step #2: • Name the anion using the –ide ending. • Example: • 1) BaF2 • Barium fluoride • *subscript does not effect the naming
Learning Check • Answers: • Sodium oxide • Magnesium iodide • Calcium bromide • Lithium sulfide • Name the following ionic compounds: a. NaO b. MgI2 c. CaBr2 d. Li2S
Writing Formulas Binary Ionic Formulas
How do we know the Ion’s Charge? • Group 1 = +1 • Group 2 = +2 • Group 13 = +3 • Group 15 Nonmetals = -3 • Group 16 Nonmetals = -2 • Group 17 = -1 • For Groups 3 -12 and Sn & Pb: • Roman Numerals equal positive charge • Example: Iron (III) = Fe+3 • Copper (II) = Cu +2
Goal = Balance charges • The sum of the positive charges must equal the sum of the negative charges. • Overall charge equals zero! • Example: • Why is calcium chloride’s formula CaCl2 not just CaCl? • Ca+2 • Cl-1 • You need 2(-1) chloride ions to balance the 1(+2) calcium ion.
Writing formulas • Example: • Magnesium fluoride • Write formulas for ions with charges. • Cation first, anion second. • Check to see if charges are balanced • Add subscripts to balance charges if necessary. • Always need lowest ratio of ions
More examples • Aluminum sulfide • Iron (III) bromide • Lithium oxide • Potassium chloride
Learning Check • Write the formulas for the following binary ionic compounds: • Manganese (III) oxide • Strontium sulfide • Calcium iodide • Chromium (VI) fluoride
Learning Check Answers • Manganese (III) oxide • Mn2O3 • 2. Strontium sulfide • SrS • 3. Calcium iodide • CaI2 • 4. Chromium (VI) fluoride • CrF6