unsur 138Angka 138 dan 137 pada 138Ba dan 137Ba menunjukkan nomor massanya. Nomor massa adalah jumlah total dari neutron dan proton. Barium memiliki nomor atom 56. Maka,Unsur 138, also known as Eka-Lawrencium, is a synthetic element with the atomic number 138. It was first predicted as part of the actinide series in the 1940s and was officially