Name the member of the Actinoid Series which is the last element:

Lawrencium (Lr)

The correct answer is option 3. Lawrencium (Lr).

The Actinoid Series, also known as the Actinide Series, is a group of chemical elements in the periodic table. These elements are part of the f-block of the periodic table and are characterized by their filling of the 5f orbitals. The series includes elements with atomic numbers ranging from 89 to 103.

1. Californium (Cf): Californium is an actinide element with the atomic number 98. It is a radioactive metal and one of the transuranium elements. Californium is primarily used in neutron sources and as a target material for the production of heavier transuranium elements.

2. Fermium (Fm): Fermium is an actinide element with the atomic number 100. It is also a radioactive metal and one of the transuranium elements. Fermium is primarily produced in nuclear reactors by neutron bombardment of lighter actinide elements. It has no significant practical applications and is mainly used for research purposes.

3. Lawrencium (Lr): Lawrencium is an actinide element with the atomic number 103. It is the last element in the actinide series and is also a synthetic radioactive metal. Lawrencium is highly unstable, and its properties are not well-characterized due to its short half-life. It is primarily produced in nuclear reactors by bombarding lighter actinide elements with atomic particles.

4. Nobelium (No): Nobelium is an actinide element with the atomic number 102. It is a synthetic radioactive metal and one of the transuranium elements. Nobelium is primarily produced in nuclear reactors by bombarding lighter actinide elements with atomic particles. Like fermium, nobelium has no significant practical applications and is mainly used for research purposes.

In summary, the Actinoid Series includes a group of radioactive elements with atomic numbers ranging from 89 to 103. These elements exhibit similar chemical properties due to the filling of the 5f orbitals. Each element in the series is synthetic, highly radioactive, and primarily used for research purposes.