al·lot·ro·py 
(ə-lŏtrə-pē)
(ə-lŏtrə-pē)n.
The existence of two or more crystalline or molecular structural forms of an element that have different chemical or physical attributes.
al′lo·tropic (ăl′ə-trŏpĭk, -trōpĭk), al′lo·tropi·cal adj.
al′lo·tropi·cal·ly adv.