Ionic Bonding (Brief version)

Ionic Bonding Two ions with opposite charges (+ and -) are attracted to each other An ionic bond is a chemical bond formed when atoms transfer electrons from one to another Metal + Non-Metal The positive ion is the one that donates the electron(s). The negative ion gains the electron(s)

Subscripts Written to the bottom right of an element to indicate the number of atoms of that element that it has. If no number is written, we assume that there is one atom. O 2

Subscripts Go only with the element it is beside unless there are parentheses. If there are parentheses, distribute the number outside the parentheses to everything inside the parentheses. Only use parentheses with polyatomic ions

O C SO Subscripts B 2 Boron 1 Carbon 3 Sulfur 2 Oxygen 12 Oxygen 2 4 3

Criss-Cross Rule To write the chemical formula for an ionic compound, write down the metal first and the non-metal second Ca Cl

Criss-Cross Rule Next, find the oxidation numbers for both compounds involved. Write the oxidation numbers next to the two elements 2+ 1- Ca Cl

Criss-Cross Rule 2+ 1- Ca Cl Ca Cl Cross the number from the superscript of one element to become the subscript of the other element. 2+ 1- Ca Cl Ca Cl 2

Example Al O

Example +3 -2 Al O

Example -2 Al O 3

Example Al O 3 2

Example Al O 3 2

Ionic Bonding with Polyatomic Ions When creating ionic compounds with polyatomic ions, pretend that the polyatomic ion is a regular ion. If there is more than one set of a polyatomic ion, use parentheses when writing the formula

Example SO 4 -3 Mg

Example +2 SO 4 -3 Mg

Example -3 Mg SO 4 2

Example Mg SO 4 3 2

Example Mg SO 4 3 2