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Lets take BrF as an example. I will go through the example and you can follow it for doing the ones you need to do.
To do Lewis Structures, first you have to know how many total valence electrons are there(meaning total valence electrons of all the atoms in the molecule). To know how many valence electrons an atom has just look at the group number of the atom.For part A) BrF, both the Br and the F are in group 7. That means they both have 7 valence electrons. 7 valence electrons of Br + 7 valence electrons of F = total valence electrons of 14.
Once you determine the number of valence electrons, you start by putting pairs of electrons on the atoms. You always put a pair of electron (meaning 2 electron). You do not put a single electron.
You start putting the pair of electrons around one of the atom on all four sides of the atom. Once you put the atom on all four sides then you will go the next atom and put the remaining pairs of electrons on that atom. You have to make sure that the numer of electrons that you put on is equal to the number of total valence electrons.
so for BrF, :Br:F: (pairs on each side and on the top and bottom).