Question

Which of the following statement is correct regarding an element having atomic number 79?

• A. Its first ionisation enthalpy is maximum in its group
• B. Its first ionisation enthalpy is minimum in its group
• C. It belongs to group 10 of periodic table
• D. It belongs to 5\(^\text{th}\) period of periodic table

Hint:

First ionisation enthalpy increases across a period and is higher for elements with a stable electron configuration, like gold.

Answer 1

The Correct Option is A

Let's analyze the given options based on the atomic number 79, which corresponds to the element Gold (Au). Gold is situated in Group 11 of the periodic table.

1. Its first ionisation enthalpy is maximum in its group: This statement is correct. Gold (Au), being a noble metal, has a high ionization enthalpy compared to other elements in the same group (Group 11: Copper (Cu), Silver (Ag), and Gold (Au)). This is because as we move down the group, the atomic size increases, but Gold has particularly strong relativistic and d-orbital effects that increase its ionization energy.
2. Its first ionisation enthalpy is minimum in its group: This statement is incorrect. As explained above, Gold has the highest first ionization enthalpy in Group 11.
3. It belongs to group 10 of the periodic table: This statement is incorrect. Gold is in Group 11, not Group 10. Group 10 contains elements like Nickel (Ni), Palladium (Pd), and Platinum (Pt).
4. It belongs to 5^th period of the periodic table: This statement is incorrect. Gold is located in the 6^th period of the periodic table.

Therefore, the correct statement regarding an element with atomic number 79 is: "Its first ionisation enthalpy is maximum in its group."