Polyatomic Ions SNC2DI/W

Polyatomic Ions We discussed the effects of too much sodium chloride in our bodies. Sodium also enters our bodies in another forms bond ionically with polyatomic ions: sodium phosphate (glue that holds a hot dog together) or sodium nitrite is suspected of causing digestive track issues that may lead to cancer. Nitrites can be found in hot dogs as sodium nitrite– that lovely pink colour. Nitrites are not all bad. Research has shown that sodium nitrite may help the heart muscle heal after a heart attack or transplant. Nitrates are very important for plant growth and as such as found in fertilizers. Too much nitrate through can be harmful to the environment and contribute to water pollution.

Polyatomic Ions Polyatomic ions are groups of atoms that tend to stay together and carry an overall ionic charge covalent bondsThe ion is typically held together with covalent bonds The polyatomic ion is capable of bonding with other ions

Polyatomic Ions to Know Below is the list of polyatomic ions you need know You have this list on your class periodic table.

Writing Formulas with Polyatomic Ions cation anion 1.Write the symbol for the cation first and the anion second 2.Write the combining capacity for each element over each of the ions (for polyatomic ions this is the same as the ionic charge) 3.Use “cross over” method and reduce numbers to lowest ratio without changing the formula for the ion Na + SO 4 2-  Na 2 SO 4 Al + OH 1-  Al(OH) 3 NH NO 3 1-  NH 4 NO 3

Naming Compounds Containing Polyatomic Ions Name of the metal first Name of the polyatomic ion second Polyatomic ions usually end in “ate” Na 2 SO 4  sodium sulphate Al(OH) 3  aluminum hydroxide NH 4 NO 3  ammonium nitrate

Oxyacids oxyacidsWhen hydrogen bonds to many of the polyatomic ions that contain oxygen, oxyacids form: –nitrate (NO 3 1- )  nitric acid (HNO 3 ) –phosphate (PO 4 3- )  phosphoric acid (H 3 PO 4 )

Homework 1.Name the polyatomic ion in each of the following compounds. Watch for the multivalent metals. [K] a)KNO 3 b) Ca(OH) 2 c) CuSO 4 d) Fe(NO 3 ) 3 e) (NH 4 ) 3 PO 4 2. Write the chemical formula for each of the following compounds. [K] a)potassium nitrateb) barium sulfatec) aluminum phosphate d)lead (II) sulfatee) copper (II) nitratef) ammonium hydroxide 3. Well water in agricultural areas is often monitored for nitrate ions because of possible health effects. Where can nitrate contamination come from on a farm? [A] 4. Write the names of the following compounds. [K] a) SnCO 3 b) K 2 S c) Fe(OH) 3 d) Mn(ClO 3 ) 2

Identifying Ions: Practice FeCl 3 Na 2 O CaO Fe 2 O 3 NaClO 3 Na 2 CO 3 Ca(ClO 3 ) 2 Mg(OH) 2