If the superscript (+/- sign on top) has no number, it is automatically 1
Changing Name to Chemical Formula
Identify the elements in the compound & their charges, then use the Criss Cross Method to determine the subscripts
Criss Cross Method
Shortcut used to determine the subscripts in chemical formulas by criss-crossing the numerical charges (superscripts) to determine the ratio
(Polyatomic) compounds have more than 2 elements; always use the Polyatomic Ions Chart; -ate, -ite, -ide tells you if it is a polyatomic ion
For elements ending in -ygen, -ogen, -ine, -orous, change the last 3/4 letters to the suffix ‘-ide’; for elements ending in -ic, change the last 2 letters to -ide
Noble Gases aren’t capable of bonding
Types of ions
Monoatomic Ions: only 1 atom
Polyatomic Ions: more than 1 atom
Ionic Compounds
Forms from Ionic bond between nonmetals (-) & metals (+)
Ions are atoms with a charge; neutral atoms gain/lose electrons
Subscripts
Represents the number of atoms
Changing Chemical Formula to Name
Retain the first element’s name, then change the 2nd element’s last 3 or 4 letters into ‘-ide’
Name to Chemical Formula(Try it yourself)
Ca2+ Cl− -> CaCl2
Li+ Cl− -> LiCl
Mg2+ P−3 -> Mg3P2
Changing Chem. Formula to Name
Retain the first element’s name, then find the polyatomic ion’s Chem Formula using the Polyatomic Ions Chart
Ionic Compounds
More than one ion is present in the compound, use parentheses for multiple polyatomic ions, add subscripts for polyatomic ions when needed
Changing Name to Chem Formula
Use the Polyatomic Ions & Criss Cross Method, add a parenthesis to indicate the presence of Polyatomic Ions, distinguish entire Polyatomic Ion as a single unit