Introduction to Actinoid Series
The actinoid series consists of 15 elements, ranging from actinium (Ac, atomic number 89) to lawrencium (Lr, atomic number 103). These elements are known for their complex electron configurations and radioactivity.
Last Element of Actinoid Series
The last element in the actinoid series is lawrencium (Lr).
Key Points about Lawrencium
- Atomic Number: Lawrencium has an atomic number of 103, making it the final element in the actinoid series.
- Position in the Periodic Table: Lawrencium is positioned in period 7 and is part of the f-block of the periodic table, specifically the actinides.
- Discovery: Lawrencium was first synthesized in 1961 by a team of scientists at the Lawrence Berkeley National Laboratory. It was named in honor of Ernest O. Lawrence, the inventor of the cyclotron.
- Properties: As a synthetic element, lawrencium is highly radioactive, and its most stable isotope, Lr-262, has a half-life of approximately 3.6 hours.
Misconceptions About Other Options
- Lutetium: While lutetium (Lu) is the last element in the lanthanide series (atomic number 71), it is not an actinoid.
- Thorium and Cerium: Thorium (Th) and cerium (Ce) belong to the actinoid and lanthanide series, respectively, but they are not the last elements.
Conclusion
Thus, lawrencium (Lr) is the correct answer as the last element of the actinoid series, highlighting its significance in the study of heavy elements and nuclear chemistry.