Transcript ppt
Polyatomic Ions Writing Formulas / Naming Compounds • A polyatomic ion is a covalent molecule that has an ionic charge. (As opposed to being a neutral molecule.) • Poly = many • Atomic = atoms • Ion = charged particle • A charged particle that consists of more than one atom. Polyatomic Ions Examples: Sulfate = SO4-2 Nitrate = NO3-1 Phosphate = PO4-3 Chlorate = ClO3-1 Carbonate CO3-2 • Notice the ending has changed to –ate. Writing Formulas Sodium Sulfate • Write the formula for the metal. Add the oxidation number from the periodic table. Na+1 • Write the formula for the polyatomic ion from the ion chart. Add its oxidation number. SO4-2 Sodium Sulfate Na +1 SO4-2 • Determine the common factor of the two oxidation numbers. In this case, 2. • Decide how many of each ion is needed to equal the common factor. In this case, 2 sodium ions and 1 sulfate ion. • Write these numbers as the subscript for each ion. Na2SO4 Calcium Phosphate • Write the formula for the metal. Add the oxidation number from the periodic table. Ca+2 • Write the formula for the polyatomic ion from the ion chart. Add its oxidation number. PO4-3 Calcium Phosphate Ca +2 PO4 -3 • Determine the common factor of the two oxidation numbers. In this case, 6. • Decide how many of each ion is needed to equal the common factor. In this case, 3 calcium ions and 2 phosphate ions. • Write these numbers as the subscript for each ion. Ca3(PO4)2 • Notice that the polyatomic ion must be placed in parenthesis or, instead of 2 phosphate ions, you would have 42 Oxygen atoms and 1 Phosphorus atom. Ca3PO42 Naming Compounds w/ Polyatomic Ions KClO3 • Write the name of the metal. Potassium • Write the name of the polyatomic ion from the ion chart. Chlorate • Name the compound. Potassium Chlorate Mg3(SO4)2 • Name the metal. Magnesium • Name the polyatomic ion from the ion chart. Sulfate • Name the compound. Magnesium Sulfate Some Additional Examples • Calcium Hydroxide Ca+2 OH-1 • The least common factor is 2. Therefore, 1 calcium ion will bond with 2 hydroxide ions to form a neutral compound. Ca(OH)2 • If you omitted the parenthesis, you would not have 2 hydroxide ions. Instead you would have 2 hydrogen atoms and one oxygen atom. CaOH2 Try these • Write names for the following compounds. CaCO3 Al2(SO4)3 Ca(ClO3)2 K3PO4 Mg(OH)2 Fe(ClO3) 3 Answers • • • • • • Calcium carbonate Aluminum sulfate Calcium chlorate Potassium phosphate Magnesium hydroxide Iron (III) chlorate Now, these! • Write formulas for the following compounds. Lithium sulfate Calcium acetate Aluminum nitrate Magnesium phosphate Sodium carbonate Vanadium (V) hydroxide Ammonium carbonate Answers • • • • • Li2SO4 Ca(C2H3O2)2 Al(NO3)3 Mg3(PO4)2 Na2CO3