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please someone explain this I dont get it at all. how do we know that the 4th electron came from 2p because it's at 4th ionisation? why is it talking about 3s?? how do overall know that aluminium is in group 3 from the table??? thanks​

please someone explain this I dont get it at all how do we know that the 4th electron came from 2p because its at 4th ionisation why is it talking about 3s how class=