周期表中的第8和第9周期的元素列表如下: **第8周期(稀有气体)** - Helium (He) - Neon (Ne) - Argon (Ar) - Krypton (Kr) - Xenon (Xe) - Radon (Rn) **第9周期(锕系元素)** - Astatine (At) - Radon (Rn) - Francium (Fr) - Radium (Ra) - Actinium (Ac) - Thorium (Th) - Protactinium (Pa) - Uranium (U) - Neptunium (Np) - Plutonium (Pu) - Americium (Am) - Curium (Cm) - Berkelium (Bk) - Californium (Cf) - Einsteinium (Es) - Fermium (Fm) - Mendelevium (Md) - Nobelium (No) - Lawrencium (Lr) - Rutherfordium (Rf) - Dubnium (Db) - Seaborgium (Sg) - Bohrium (Bh) - Hassium (Hs) - Meitnerium (Mt) - Darmstadtium (Ds) - Roentgenium (Rg) - Copernicium (Cn) - Nihonium (Nh) - Flerovium (Fl) - Moscovium (Mc) - Livermorium (Lv) - Tennessine (Ts) - Oganesson (Og)