how do you tell the difference between an ionic or a molecular compound?

Question

thanks

Answer 1

Ionic compounds are hard, high melting point solids. Molecular compounds, for the most part, are soft and low melting compounds. (Diamond is an exception--It is very hard but is not ionic).

Answer 2

so if i gives me CO how would i know what it is if i cant look up the hardness or softness? i can just look at the periodic table

Answer 3

I didn't know how to answer the question because I didn't know if you were looking at physical properties OR if you were trying to predict which is which. I take it you wanted the latter. To know if you have an ionic or covalent compound you want to look up the electronegativities of the elements. For CO or CO2 you find C = about 2.5 and O about 3.5; the difference is about 1.0. If the difference is about 1.7 or 1.8 it is 50% ionic/50% covalent. Compounds with more than 50% ionic character usually are called ionic and those with less than 50% ionic character are called covalent.
Cs with about 0.8 and F with about 4.0 gives 3.2 difference which makes it an ionic compound. H coupled with H to make H2 or N with N to make N2 have differences of zero which makes them purely covalent. There are few compounds that are 1OO% covalent or 100% ionic; those, if we want to be a little more precise, would be called polar covalent (CO and CO2 are examples of polar covalent compounds).