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Groups say the valence number. For example Hydrogen is on group 1, has 1 electron on it's last and only level. So we can know the valence number on that are on the groups 1-2 and 13-18. But how am I supposed to know the valence number on transition metals(3-12)?

PD: You could tell me to use the oxidation number but that is completely wrong since they are not the same.


marked as duplicate by bon, M.A.R., Wildcat, orthocresol, Geoff Hutchison Dec 4 '15 at 16:23

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