Also look for the structures of N2O and COCl2 in the net - there are things that you cannot guess correctly unless you have a deep understanding of Molecular Orbital theory (or more which is usually needen have done necessary calculations/have found necessary experimental evidence) that comes at university level. But that is all just lyrics.
Basic idea of Lewis structures is that electrons of different elements tend to pair when forming molecules. For example in RbF Rb atom pairs it's only electron with one of the electrons on fluorine, one bond forms and the latter is left with 7-1=6 electrons that form 3 lone pairs. The same is true for sulfate ion (see picture) where sulfur pairs all of it's six electrons with those coming from the oxygen and the remaining electrons on the oxygen atoms form lone pairs.
You can see that K is in group 1 of the periodic table because it has 1 electron at it's outer orbital, while Sr and Ca are in group 2 because they have 2 electrons - take this into account and try once more for K2O, CaBr2 and SrO.
You should be able to correct BN2- and ClO4- structures as well.
Many useful examples can be found here:
http://www.shodor.org/unchem/basic/lewis/index.htmlAnd generally use net to get information - it is a powerful tool. Good luck.
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Topic: General Chemistry - Lewis Structure (Read 9184 times)