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Naming and Writing Formulas for Ionic Compounds. Names and Formulas Chapter 9 Section 2. Vocabulary. Binary Compound A compound composed of two elements; NaCl and Al 2 O 3 are binary compounds. State Standard. 4.6
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Naming and Writing Formulas for Ionic Compounds Names and Formulas Chapter 9 Section 2
Vocabulary • Binary Compound • A compound composed of two elements; NaCl and Al2O3 are binary compounds
State Standard • 4.6 • Name and write the chemical formulas for simple ionic and molecular compounds, including those that contain the polyatomic ions, carbonate, hydroxide, nitrate, phosphate, and sulfate
Writing Formulas for Binary Compounds • To write the formula of a binary ionic compound, first write the symbol of the cation and then the anion. Then add subscripts as needed to balance the charges. • Example • K+ and Cl- • K+Cl- • KCl
Writing Formulas for Binary Compounds • Another approach to writing a balanced formula for a compound is to use the crisscross method. • The numerical value of the charge of each ion is crossed over and becomes the subscripts for the other ion.
Naming Binary Compounds • To name any binary ionic compound, place the cation name first, followed by the anion name. • Example • KCl • Potassium is the cation • Chloride is the anions • Potassium chloride
Naming Binary Compounds • If the metallic element in a binary ionic compound has more than one common ionic charge, a Roman numeral must be included in the cation name. • Example, tin (Sn) • Sn3+ and F- • Tin (III) fluoride, SnF3 • Sn4+ and O2- • Tin (IV) oxide, Sn2O3
Compounds with Polyatomic Ions • To write the formula for a compound with a polyatomic ion, first write the symbol (or formula) for the cation followed by the symbol (or formula) for the anion. Then, add subscripts as needed to balance the charges.
Writing Formulas for Compounds with Polyatomic Ions • Whenever more than one polyatomic ion is needed to balance the charges in an ionic compound, use parentheses to set off the polyatomic ion in the formula.
Naming Compounds with Polyatomic Ions • To name a compound containing a polyatomic ion, state the cation name first and then the anion name. If the cation is a metallic element that has more than one common ionic charge, include a Roman numeral in the cation name. • Example • NH4+ and OH- • Ammonium and hydroxide • Ammonium hydroxide, NH4OH
Summary • To write the formula of a binary ionic compound, write the symbol of the cation and then the anion. Then balance the charges. The name of a binary ionic compound is the cation name followed by the anion name. • To write formula for compounds with polyatomic ions, write the symbol for the cation followed by the symbol for the anion. Then balance the charges. To name a compound containing a polyatomic ion, state the cation name followed by the anion name.