pe·ri·o·dic·i·ty 
(pîr′ē-ə-dĭsĭ-tē)
(pîr′ē-ə-dĭsĭ-tē)n. pl. pe·ri·o·dic·i·ties
1. The quality or state of being periodic; recurrence at regular intervals.
2. The repetition of similar properties in chemical elements, as indicated by their positioning in the periodic table.