Draw the lewis dot diagram for the following atoms F He S
any ideas on F? based on its location on the ptable how many valence electrons do you think it has? as a reminder these are neutral atoms, not ions
7
awesome, so you'd draw 7 electrons (3 pairs of 2, plus 1 leftover)
thoughts on helium?
2
good helium is a special case, it only has a 1s orbital so the electrons have to be paired up
thoughts on sulfur?
6
good sulfur follows the normal rule for pairing, fill up 4 electrons separately then pair up the last 2
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CH4
any ideas? have you tried adding up all the valance electrons for 1 carbon 4 hydrogens?
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perfect
But isn't there dots
there are no free electrons so there shouldn't be any
this is a covalent compound so all the bonds involved shared electrons, represented by the lines
Sel2
thoughts? any attempts to add up the valence electrons?
well, anyway, selenium has 4 valence e's and each iodine has 7, so 6 + 7 + 7 = 20, divide by 2 to get 10 electron pairs so set up your compound where Se is in the middle, and I is bonded to the left and right, and fill up enough lone pairs so that the whole compound has 10 electron pairs total
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that's only five pairs, so you gotta fill up the iodine atoms completely to get 10 total pairs
10 total pairs = 20 total electrons
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almost just one more bond on the first SeI
also when you make a double bond you have to erase an electron pair
... wait
but thats still 16 :(
oh, of course, selenium has an expanded octet so it can actually take more than 8, so put the last electrons on the selenium atom itself
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I3^-
well, each iodine gives 7, so 3*7, then you gotta add 1 because we have a -1 charge, so 22 electrons or 11 pairs
as a hint this one only has single bonds
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yeah that should be it, just two things 1. the pair of electrons on the right side shouldn't be in between the bond, they need to be off to the right side 2. since this is an ion you also need to draw a set of brackets around the whole thing, and write the charge at the top right
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yup good
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