A chemistry question asks which of the following has three lone pairs of electrons around the central atom and the possible multiple choice answers include BF2 -
(2 flourines and a negative charge) and CIF2 - ? I thought only a metal and non metal could form an ionic bond? do I not know this because I've just started year 12 and I haven't learnt of this yet?
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How can two non metals bond and form an ion? watch
- Thread Starter
- 29-10-2017 16:19
- 29-10-2017 16:28
It’s not ionic bonding that the question is about, the answer is ClF2 - because the Cl is in group 7 so naturally has 7 outer electrons, when bonded to two other atoms it would have 2 lone pairs and a free radical (don’t worry if you haven’t learnt this yet because you will) adding another electron causes the free radical to just become another line pair whilst giving an overall charge or -1 because of the extra electron
- 29-10-2017 16:36
ClF2- will have 3 lone pairs of electrons around the central atom (Cl). This is because chlorine has 7 valence electrons (it's in group 7), and flourine has 7 valence electrons, and there's two of them. There's also a negative charge, meaning there's one extra electron.
Add the number of electrons up, you get 22 electrons. A full outer shell will have 8 electrons, so if you take away the highest multiple of 8 under the number of electrons (22), you get 16. 22-16=6. So there are 6 electrons unpaired around the central atom, but they exist in pairs, so 6/2=3. There are 3 lone pairs.
If you draw the dot and cross structure of ClF2- you will see this shown more clearly. Also, these compounds do not have ionic bonding, they show covalent bonding, they share electron pairs.