Naming Ionic Compounds

Ions Getting Together Demos Pb 2+ ions in Water (CLEAR) I - ions in Water (CLEAR) PbI 2 (YELLOW)

Ions Getting Together Demos Cu 2+ ions in Water (Transparent Blue) OH - ions in Water (CLEAR) Cu(OH) 2 (Light Blue)

Ionic Compounds - Writing Formulas An ionic compound consists of a metal and a non-metal. Metals lose electrons to form positive ions called cations. Non-metals gain electrons to form negative ions called anions. Ionic compounds stick together because of the attraction between cations and anions. An ionic compound consists of a metal and a non-metal. Metals lose electrons to form positive ions called cations. Non-metals gain electrons to form negative ions called anions. Ionic compounds stick together because of the attraction between cations and anions.

Writing Formulas Ionic compounds are neutral compounds, therefore the positive charges must equal the negative charges. For example, draw the ionic bond between Magnesium and Fluorine….. Ionic compounds are neutral compounds, therefore the positive charges must equal the negative charges. For example, draw the ionic bond between Magnesium and Fluorine…..

Magnesium + Fluorine Mg F F Mg 2+ F -1 F -1 The formula is MgF 2

Writing Formulas An easier way to determine the formula of an ionic compound without drawing the bond structure is to make sure that the positive charges are equal to the negative charges.

Steps to Finding Formulas for Ionic Compounds 1) Write the element symbol with the charge of the ion next to it. You can find the charges of the ions from the periodic table of ions on the back of your periodic table.

Steps to Finding Formulas for Ionic Compounds 2) If the charges are already equal, just write the formula as is. E.g. Magnesium + Oxygen Mg 2+ O 2- --> MgO 2) If the charges are already equal, just write the formula as is. E.g. Magnesium + Oxygen Mg 2+ O 2- --> MgO

Steps to Finding Formulas for Ionic Compounds 3) If the charges are NOT equal, add cations and anions to make the charges equal. E.g. Magnesium + Fluorine Mg 2+ F 1- F 1- --> MgF 2 3) If the charges are NOT equal, add cations and anions to make the charges equal. E.g. Magnesium + Fluorine Mg 2+ F 1- F 1- --> MgF 2

Balancing Charges E.g. Potassium + Nitrogen K 1+ K 1+ K 1+ N > K 3 N E.g. Potassium + Nitrogen K 1+ K 1+ K 1+ N > K 3 N

The Criss - Cross Rule Make the charge of the cation the subscript of the anion. Make the charge of the anion the subscript of the cation. Let’s look an an example…. Make the charge of the cation the subscript of the anion. Make the charge of the anion the subscript of the cation. Let’s look an an example….

Calcium + Nitrogen Ca 2+ N 3- Now Criss Cross Ca 3 N 2 Ca 2+ N 3- Now Criss Cross Ca 3 N 2

More Examples Well do some examples together on the overhead. Then we’ll play a chemistry game!! Well do some examples together on the overhead. Then we’ll play a chemistry game!!