10. Periodic Properties of the Elements
Valence Electrons of Elements
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Here it says, how many valence electrons would the manganese 5 ion possess? So manganese 5 means it has a 5 plus or plus 5 charge. That means that it has lost 5 electrons. So remember, manganese is a transition metal, it is in group 7 of the periodic table. Don't confuse group 7 with group 7 a. Group 7 a are the halogens. Right? But you're talking about group 7 for this man manganese ion. So here for manganese when it's neutral it has 7 valence electrons, but it just lost 5, so we're gonna subtract out 5. So it should have 2 valence electrons left. If you wanted to do it the longer way through the use of the electron configuration, you could also do that. So here we need to find out what the electron configuration is of the neutral manganese. It would be argon4s23d5. Now remember, plus 5 means we would lose 5 electrons, and we lose them from the high shell number first. So we'd lose 2 both of these electrons from 4 s so they'd be completely gone, and we need to lose 3 more to get to plus 5 charge. Those additional 3 would have to come from the 3 d set of orbitals. So when we lose 3 more, we'd have left 2 electrons. Remember, the number of valence electrons for a transition metal is the s+orbitalelectrons. We lost our 4sorbitalelectrons, so all we have left are these 2 d orbital electrons. So whether you do it the long way through the electron configuration, or if you just simply remember the secondary group number for the transition metals is equal to their valence electrons, you'd also find out that you have 2 valence electrons left. So choose the way that you're most comfortable with to get your final answer.
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