There is a simple and easy way to identify ionic versus covalent compounds.
Ionic compounds can be of the following types:
1. Metal + Nonmetal
To figure out whether an element is a metal or a nonmetal, look at the Periodic Table. Elements on the right of the staircase on the periodic table are metals. Elements to the left of the staircase on the periodic table are nonmetals. Hydrogen is a nonmetal even though it is located on the right side.
Examples: KCl, BaS
2. Metal + Polyatomic ion
Polyatomic ions are ions that are made of multiple atoms.
Students taking chemistry regent exam can find a list of polyatomic ions in Table E on the reference table.
Examples: KNO3, Mg(OH)2
3. Polyatomic ion + Polyatomic ion
Two polyatomic ions will also form ionic compounds.
4. Polyatomic ion + Nonmetal
This is probably the most rare case of ionic compounds.
Covalent compounds are easy to identify. A covalent compound consists of two or more nonmetals.
Examples: CO2, SO4, C6H12O6
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