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Would we need to know how to identify compounds such as ammonium chloride and draw the lewis structure without knowing the formula? I also had trouble figuring out which bonds were covalent and which were ionic without seeing the charges on the formula. (NH4+ CL-)
I think I remember Professor Lavelle saying that we would almost always be given the formula, but it may help to memorize some common ions, prefixes, and suffixes. To find out which bonds are ionic vs. covalent, I believe you'd have to look at the components of each compound and compare it to what we've learned about characteristics of the different types of bonds (like covalent bonds are between nonmetals, ionic bonds are metals and nonmetals, main group metals usually form cations, etc.). You can use periodic trends to help you remember what charge different atoms generally take on.
As for right now, I think we would be given formulas for the compounds. However, in the future we may need to memorize some of the most common ions and polyatomic ions. As the previous comment mentioned, you can usually determine whether a bond is ionic or covalent based on the classification of each element (metal, nonmetal, metalloid). However, you can also determine which compounds are ionic and which are covalent using the elements' electronegativities. You find the difference between two elements' electronegativities and if the difference is greater than 2, the bond is usually ionic. If it is less than 1.5, then it is usually covalent. Based on the classifications of each of the bonds within a compound, you can determine whether the compound as a whole is ionic or covalent.
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