The element having lowest `IE_(1)`

Options

A. Fe
B. Co
C. Ni
D. Cu

Answer

To determine the element with the lowest first ionization energy (IE₁), we can follow these steps:

### Step 1: Understand Ionization Energy
Ionization energy is defined as the minimum energy required to remove an electron from an isolated gaseous atom in its ground state. The first ionization energy (IE₁) refers to the energy required to remove the first electron.

**Hint:** Remember that ionization energy generally increases across a period and decreases down a group in the periodic table.

### Step 2: Consider the Elements in the d-block
The question involves d-block elements, specifically focusing on transition metals. Common transition metals include Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), and Zinc (Zn).

**Hint:** Identify the elements in the d-block and their respective positions in the periodic table.

### Step 3: Analyze Trends in Ionization Energy
1. **Size and Charge:** Ionization energy is inversely related to the atomic size; larger atoms have lower ionization energies because their outer electrons are further from the nucleus and experience less nuclear charge.
2. **Effective Nuclear Charge (Z-effective):** As you move across a period, the effective nuclear charge increases, leading to higher ionization energies.

**Hint:** Consider how the atomic size and effective nuclear charge influence the ionization energies of the d-block elements.

### Step 4: Compare the Ionization Energies of Selected d-block Elements
- **Iron (Fe)**: [Ar] 4s² 3d⁶
- **Cobalt (Co)**: [Ar] 4s² 3d⁷
- **Nickel (Ni)**: [Ar] 4s² 3d⁸
- **Copper (Cu)**: [Ar] 4s² 3d¹⁰

From the analysis, we find that:
- Iron has a relatively higher ionization energy due to its electron configuration.
- Cobalt has a slightly lower ionization energy than Iron.
- Nickel has a higher ionization energy than Cobalt.
- Copper, despite having a filled d-subshell, exhibits a lower ionization energy than expected due to electron-electron repulsion and shielding effects.

**Hint:** Look for exceptions in the trends, especially in transition metals where electron configurations can lead to unexpected results.

### Step 5: Identify the Element with the Lowest IE₁
Based on the trends and exceptions discussed, Copper (Cu) is found to have the lowest first ionization energy among the d-block elements mentioned.

**Final Answer:** The element with the lowest first ionization energy (IE₁) is Copper (Cu).