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Naming Compounds and Writing Formulas for Ionic Compounds Chapter 9 Section 2.

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Presentation on theme: "Naming Compounds and Writing Formulas for Ionic Compounds Chapter 9 Section 2."— Presentation transcript:

1 Naming Compounds and Writing Formulas for Ionic Compounds Chapter 9 Section 2

2 Naming Binary Ionic Compounds Composed of two elements Cation name followed by anion name ▫NaF ▫CaCl 2 ▫Li 3 N ▫Sodium fluoride ▫Calcium chloride ▫Lithium nitride

3 Naming Binary ionic compounds with transition metals Recall transition metal ions have multiple charges First start with ion that only has one possible charge ▫“position of strength” Then determine transition metal ionic charge. Example: CuO ▫Copper and oxygen ▫Copper can be +1 or +2… ▫…but Oxygen is always -2. Position of strength! ▫1:1 ratio means this copper must be +2 to cancel out the -2 of the oxygen atom. ▫Copper (II) oxide

4 You try it! SnS 2 FeCl 3 SnF 2 CuI 2 CoI 2 CuI Tin (IV) sulfide Iron (III) chloride Tin (II) fluoride Copper (II) iodide Cobalt (II) iodide Copper (I) iodide

5 Writing Formulas for Binary Ionic Compounds Write the symbol for the cation followed by the symbol for the anion. Add whatever subscripts are needed to balance the charges. Potassium chloride Calcium bromide

6 A little trickier… Iron (III) oxide ▫Iron (III) is Fe 3+ ▫Oxide is O 2- How do you balance this? Crisscross method, or finding the least common multiple method.

7 Iron (III) Oxide (Rust) ▫LCM Method ▫3x2 = 6 (least common multiple) ▫Two Fe 3+ cations have a net charge of:  +6 ▫Three O 2- anions have a net charge of:  -6 ▫Balanced formula for Iron(III) Oxide is Fe 2 O 3

8 Numerical charge of each ion is crossed over and used as a subscript for the other ion The signs of the numbers are dropped. Fe 3+ O 2- Fe 2 O 3 2(3+) + 3(2-) = 0 Crisscross Method

9 Crisscross doesn’t always work… Calcium Sulfide Ca 2+ S 2- Ca 2 S 2 Remember: formulas for ionic compounds show the lowest whole-number ratios of ions The correct formula for Calcium sulfide is CaS 1(2+) + 1(2-) = 0 Crisscross method unnecessary in this case

10 Ternary Ionic Compounds Ternary Compound: A compound that contains atoms of 3 different elements ▫Most ternary ionic compounds contain a polyatomic ion ▫THIS IS WHY YOU NEED TO HAVE THEM MEMORIZED!!! You need to recognize polyatomic ions quickly

11 Example: write the formula from the name How would you write the formula for calcium nitrate? Write the formula (symbol and charge) for each ion Balance the charges (hint: use crisscross here) Ca 2+ and NO 3 - Ca(NO 3 ) 2 Include parenthesis around the polyatomic ion followed by the subscript of how many of those ions are needed to balance the charge of the compound

12 More examples ▫If you only need one of the polyatomic ions to balance the charge of the compound, you do not need to use parentheses ▫Calcium Carbonate  Ca 2+ and CO 3 2-  CaCO 3  No parentheses ▫Strontium Sulfate  Sr 2+ and SO4 2-  SrSO 4 ▫Lithium Carbonate  Li + and CO 3 2-  Li 2 CO 3

13 Potassium Sulfate ▫K + andSO 4 2- ▫K 2 SO 4 Magnesium Hydroxide ▫Mg 2+ and OH - ▫Mg(OH) 2 Write the formulas for the following

14 Name the cation first, followed by the anion Determine the charge of the polyatomic ion. Balance the polyatomic anion by adding an appropriate subscript for the cation. K 2 Cr 2 O 7 Composed of K + and Cr 2 O 7 -2 potassium dichromate Naming Ternary Ionic Compounds

15 LiCN ▫Lithium Cyanide Sr(H 2 PO 4 ) 2 ▫ Strontium dihydrogen phosphate (NH 4 ) 2 C 2 O 4 ▫ Ammonium Oxalate Fe(ClO 3 ) 3 ▫ Iron (III) Chlorate Name the following Compounds


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