The first ionisation energies of the elements of the first transition series `(TitoCu)`

Options

A. increases as the atomic number increases
B. decreases as the atomic number invreases
C. do not show any change as the addition of electrons takes place in the inner (n- 1) d orbitals
D. increases from Ti to Mn and then decreases from Mn to Cu.

Explanation

To solve the question regarding the first ionization energies of the elements of the first transition series (from Titanium to Copper), we will analyze the trends in ionization energy as we move across the series. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Elements in the Series
The first transition series includes the following elements: Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu).

### Step 2: Identify the Trends in Ionization Energy
As we move from Titanium (Ti) to Copper (Cu), we need to consider two main factors that affect ionization energy:
- **Nuclear Charge**: The number of protons in the nucleus increases as we move across the period.
- **Atomic Size**: The atomic radius generally decreases due to increased nuclear charge, which pulls the electrons closer to the nucleus.

### Step 3: Analyze the Effect of Nuclear Charge and Atomic Size
- **Increase in Nuclear Charge**: As we move from Ti to Cu, the nuclear charge increases because the atomic number increases. This means that there is a greater positive charge in the nucleus, which can attract the electrons more strongly.
- **Decrease in Atomic Size**: The atomic radius decreases as the electrons are pulled closer to the nucleus due to the increased nuclear charge. A smaller atomic size means that the outermost electrons are held more tightly by the nucleus.

### Step 4: Conclusion on Ionization Energy Trend
Due to the combined effect of increasing nuclear charge and decreasing atomic size, the first ionization energy generally increases from Titanium to Copper. Therefore, the correct conclusion is that the first ionization energy increases as we move from Ti to Cu.

### Final Answer
The first ionization energies of the elements of the first transition series (from Titanium to Copper) **increase** as the atomic number increases.

---