▁of ▁b onds ▁are ▁s igma ▁b onds ▁( us ually ▁formed ▁by ▁hy brid ▁orbit als ) ▁and ▁pi ▁b onds ▁( formed ▁by ▁un hy brid ized ▁p ▁orbit als ▁for ▁atoms ▁of ▁main ▁group ▁elements ). ▁ ▁The ▁geometry ▁can ▁also ▁be ▁understood ▁by ▁mole cular ▁orb ital ▁theory ▁where ▁the ▁electrons ▁are ▁del ocal ised . ▁ ▁An ▁understanding ▁of ▁the ▁w av eli ke ▁behavior ▁of ▁electrons ▁in ▁atoms ▁and ▁mole cules ▁is ▁the ▁subject ▁of ▁quantum ▁chem istry . ▁ ▁Is om ers ▁▁ ▁Is om ers ▁are ▁types ▁of ▁mole cules ▁that ▁share ▁a ▁chemical ▁formula ▁but ▁have ▁difference ▁geomet ries , ▁resulting ▁in ▁different ▁properties : ▁ ▁A ▁pure ▁subst ance ▁is ▁composed ▁of ▁only ▁one ▁type ▁of ▁is omer ▁of ▁a ▁mole c ule ▁( all ▁have ▁the ▁same ▁geomet rical ▁structure ). ▁ ▁Struct ural ▁is om ers ▁have ▁the ▁same ▁chemical ▁formula ▁but ▁different ▁physical ▁arrang ements , ▁often ▁forming ▁alternate ▁mole cular ▁geomet ries ▁with ▁very ▁different ▁properties . ▁The ▁atoms ▁are ▁not ▁bond ed ▁( connected ) ▁together ▁in ▁the ▁same ▁orders . ▁ ▁Function al ▁is om ers ▁are ▁special ▁kinds ▁of ▁struct ural ▁is om ers , ▁where ▁certain ▁groups ▁of ▁atoms ▁exhib it ▁a ▁special ▁kind ▁of ▁behavior , ▁such ▁as ▁an ▁ ether ▁or ▁an ▁alco hol . ▁ ▁S tere ois om ers ▁may ▁have ▁many ▁similar ▁phys ico chem ical ▁properties ▁( mel ting ▁point , ▁bo iling ▁point ) ▁and ▁at ▁the ▁same