Effective nuclear charge `(Z_(eff))` is the net attractive force on electrons under consideration and is equal to:
`Z_(eff) = Z - sigma` (nuclear charge - screening constant). `Z_(eff)` or `sigma` is calculated by Slater's formula, as given.
If one electrons is present in the outermst orbit, there will be no screening in that orbital. Each electrons contribute, `0.35` (total electrons minus one electron) present in the outermost shell.
A contribution of `0.85` for each electrons is taken in the `(n - 1)th` shell.
Which of the following statement is wrong?

Options

A. The number of lobes in `f`-orbitals are `8`.
B. `IE_(1)` of elements increases along the period.
C. `IE_(1)` of the group `3` elements is more than that of the group `2` elements.
D. `IE_(1), IE_(2)` and `IE_(3)` of an elemnt are `9.5, 18.5` and `154.4 eV`. Predict that the element has either two `s`-electrons or two `p`-electrons in the valence shell.

Explanation

To determine which statement is wrong regarding effective nuclear charge and ionization energy, we will analyze each statement based on the principles of atomic structure and periodic trends.

### Step-by-Step Solution:

1. **Understanding Effective Nuclear Charge (Z_eff)**:
- The effective nuclear charge is calculated using the formula:
\[ Z_{eff} = Z - \sigma \]
- Where \(Z\) is the actual nuclear charge (number of protons) and \(\sigma\) is the screening constant.

2. **Analyzing the Statements**:
- **Statement A**: "The number of lobes in f orbital are eight."
- This statement is true. The f orbitals can have a maximum of 7 lobes, but when considering the total number of orbitals available, it is correct to say there are 8 lobes when including the different orientations.

- **Statement B**: "Ionization energy of element increases along the period."
- This statement is also true. As you move from left to right across a period, the ionization energy generally increases due to the increase in nuclear charge and decrease in atomic radius.

- **Statement C**: "Ionization energy IE1 of group 3 element is more than that of group 2 element."
- This statement is incorrect. Generally, the ionization energy of group 2 elements (like Magnesium) is higher than that of group 3 elements (like Aluminum) because group 2 elements have a filled s subshell, which provides extra stability, making it harder to remove an electron compared to group 3 elements which have one electron in the p subshell.

- **Statement D**: "IE1, IE2, IE3 of element are given 9.5, 18.5 and 154.4, which means that IE3 is drastically higher."
- This statement is true. A large jump in ionization energy values indicates that the electron being removed comes from a more stable, filled shell, suggesting that the element has either 2s or 2p electrons.

3. **Conclusion**:
- The wrong statement among the options provided is **Statement C**.

### Final Answer:
The wrong statement is **C**: "Ionization energy IE1 of group 3 element is more than that of group 2 element."