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My textbook states,
Period 2 elements typically obey the octet rule. Period 3 and later elements can expand their valence shells. Elements in Periods 5 and 6 of the p-block show variable valence (the inert-pair effect).
I was surprised that it said period 2 elements typically obey the octet rule. What are some circumstances in which period 2 elements break the octet rule? I though they couldn't because they don't have available d orbitals.