A hypothetical element composed only of neutrons has also been proposed and would have atomic number 0.
ɐ hˌaɪpəθˈɛɾɪkəl ˈɛlɪmənt kəmpˈoʊzd ˈoʊnli ʌv nˈuːtɹɑːnz hɐz ˈɔːlsoʊ bˌɪn pɹəpˈoʊzd ænd wʊdhɐv ɐtˈɑːmɪk nˈʌmbɚ zˈiəɹoʊ.