Ithebula le-periodic (isiNgisi: Periodic Table), liyisibonakaliso sethebula sezinto zamakhemikhali, ezihlelwe ngenombolo ye-athomu, ukumiswa kwe-electron, kanye nezakhiwo zamakhemikhali eziphindaphindayo. Isakhiwo setafula sikhombisa ukuthambekela kwezikhathi ezithile. Imigqa eyisikhombisa yetafula, ebizwa ngokuthi izinkathi, imvamisa inezinsimbi kwesobunxele nezingezona ezikagesi ngakwesokudla. Amakholomu, abizwa ngamaqembu, aqukethe izinto ezinokuziphatha okufanayo kwamakhemikhali. Amaqembu ayisithupha amukele amagama kanye nezinombolo abazinikiwe: isibonelo, izakhi zeqembu eziyi-17 zingama-halogen; kanti iqembu le-18 lingamagesi ahloniphekile. Kuboniswe nezindawo ezine ezilula zonxande noma amabhlogo ahlobene nokugcwaliswa kwama-orbitals e-athomu ahlukile.