Lambar atomic 77 tana nufin sinadarin Iridium, wanda ke da protons 77 a tsakiyan atomic. Lambar atomic tana wakiltar adadin protons da ke cikin tsakiya na zarra na wani element. A cikin zarra mai tsaka-tsaki, lambar atomic shima yayi daidai da adadin electrons da ke kewaya tsakiya. Iridium karfe ne mai kauri, mai wuya, fari-fari na mika mulki tare da babban wurin narkewa kuma ana amfani da shi a aikace-aikace masu zafi, kamar a cikin tartsatsin walƙiya, crucibles, kuma azaman mai taurara don kayan kwalliyar platinum.