How can you tell the difference between an ionic and covalent molecule NAME?
As a rule metal + non metal forms an ionic compound and non metal + non metal forms a covalent compound. Also ionic compounds are hard solids with usually high or very high melting and boiling points while covalent compounds are gases or liquids or soft solids with low melting and boiling points eg a gas or liquid can only be a covalent compound. Using the above physical properties we can decide whether a compound is ionic or covalent. However giant covalent molecules eg diamond or quartz are hard high melting point solids and some metals with small atomic radius eg beryllium and aluminium, form not ionic but covalent compounds. Finally ionic compounds have names ending in -ide eg magnesium chloride, sodium sulfide or in -ate if they contain oxygen with another atom in a negative ion eg potassium sulfate which contains the negative SO4 2- ion attached to a positive K+ ion.
