Question

The last element of actinide series is:
a.) Thorium
b.) Cerium
c.) Lawrencium
d.) Lutetium

Answer 1

In order to solve the given problem we will first see in brief about the actinide series, we will also see the position of the actinide series in the periodic table and why the name given to the series is actinide. We will further see all the elements present in this series in the arranged order. Further with the help of the series we will find the last element of the actinide series. We will also see in brief about this element, its occurrence and uses.

Complete step by step answer:
Series of actinides is a collection of radioactive metallic elements from the periodic table in Group 3. Series members are sometimes referred to as actinides. The 15 elements with the atomic numbers 90 through 103 are still included in the sequence. Rare Earth Metals are present in both of the Lanthanide and Actinide Series. All these items have a high variety of oxidation numbers and are all radioactive. The radioactivity of the elements of actinide is due to their nuclear volatility. The nucleus of an actinide portion undergoes radioactive decay to become more stable, emitting gamma rays, alpha particles, beta particles, or neutrons.
This series is present at the end of the periodic table in a separate column. Due to the presence of actinium as the first element of the group, we have the name actinides.
The elements present in the actinide series in order with their atomic number is:
89. Actinium
90. Thorium
91. Protactinium
92. Uranium
93. Neptunium
94. Plutonium
95. Americium
96. Curium
97. Berkelium
98. Californium
99. Einsteinium
100. Fermium
101. Mendelevium
102. Nobelium
103. Lawrencium

So, we can see that the last element of the actinide series is Lawrencium.
With the symbol Lr (formerly Lw) and the atomic number 103, Lawrencium is a synthetic chemical compound. It is named in honour of the inventor of the cyclotron, Ernest Lawrence, a method that was used to explore several nuclear artificial elements.
It is often known as the product in an actinide and is toxic. There are no practical applications of lawrencium at present, other than in research. In time, this part could be used for technology and energy harvesting purposes.
Hence, the last element of the actinide series is Lawrencium.
So, the correct answer is “Option C”.

Note: In order to solve such types of problems students must remember some common elements of these special series. It is hard to remember the entire element but students should try to remember at least the starting and the end element of the series. And students must remember the position of the series in order to find the element on the periodic table.