Question

Which one of the following is correct for all elements from Sc to Cu ?

• A. The lowest oxidation state shown by them is +2
• B. 4S orbital is completely filled in the ground state
• C. 3d orbital is not completely filled in the ground state
• D. The ions in +2 oxidation states are paramagnetic

Answer 1

The Correct Option is D

Let's evaluate each option:

• (A) The lowest oxidation state shown by them is +2: This is incorrect. The lowest oxidation state of elements like Scandium (Sc) is +3, not +2.
• (B) 4s orbital is completely filled in the ground state: This is incorrect. The 4s orbital is not completely filled in all elements from Sc to Cu. For example, Ti has only one electron in the 4s orbital in the ground state.
• (C) 3d orbital is not completely filled in the ground state: This is incorrect. The 3d orbital is not completely filled in many elements from Sc to Cu in their ground state.
• (D) The ions in +2 oxidation states are paramagnetic: This is correct. Most of the transition metals from Sc to Cu, when in the +2 oxidation state, have unpaired electrons in their d orbitals, making them paramagnetic.

Therefore, the correct answer is (D) : The ions in +2 oxidation states are paramagnetic.

Answer 2

To solve this problem, we need to evaluate the oxidation states, electron configurations, and magnetic properties of elements from Scandium (Sc) to Copper (Cu), which range from atomic numbers 21 to 29.

1. Understanding the Oxidation States:
Elements from Sc to Cu exhibit a variety of oxidation states, with +2 being a common oxidation state. However, the lowest oxidation state varies for each element in this range. For example, Sc has a +3 oxidation state as its most stable state, while others like Mn and Fe can show oxidation states lower than +2.

2. Electron Configurations:
Elements from Sc to Cu have electron configurations that fill the 4s and 3d orbitals. In their ground states, the 4s orbital is filled first, but the 3d orbital is not always completely filled. For example, Copper (Cu) has an electron configuration of [Ar] 3d¹⁰ 4s¹, where the 4s orbital has only one electron while the 3d orbital is fully filled.

3. Assessing Each Option:
- Option (A): "The lowest oxidation state shown by them is +2" is incorrect because some elements like Scandium (Sc) exhibit a +3 oxidation state, which is lower than +2. 
- Option (B): "4s orbital is completely filled in the ground state" is incorrect because, for elements like Copper (Cu), the 4s orbital is not completely filled (Cu has 4s¹). 
- Option (C): "3d orbital is not completely filled in the ground state" is correct for most elements in this range. For example, in Copper (Cu), the 3d orbital is completely filled, but for other elements like Titanium (Ti), the 3d orbital is not fully filled. 
- Option (D): "The ions in +2 oxidation states are paramagnetic" is correct. In the +2 oxidation state, many of these ions have unpaired electrons in their 3d orbitals, making them paramagnetic, such as in Fe²⁺ and Cu²⁺.

Final Answer:
The correct answer is (D) "The ions in +2 oxidation states are paramagnetic."