Which orbital electrons are known to shield the nuclear charge improperly? Does this enerate some irregularity in properties of elements?

Explanation

### Step-by-Step Solution

1. **Understanding Shielding Effect**:
- Electrons in an atom can shield the outer electrons from the full effect of the nuclear charge (the positive charge of the nucleus). This is known as the shielding effect.

2. **Identifying the Orbitals**:
- The electrons in the d and f orbitals are known to shield the nuclear charge improperly. This is primarily due to their unique electron configurations and the shapes of the d and f orbitals.

3. **Reason for Improper Shielding**:
- The d and f orbitals have a more complex and scattered structure compared to s and p orbitals. This scattered structure leads to less effective shielding of the nuclear charge, resulting in what is termed "overshielding."

4. **Consequences of Poor Shielding**:
- The improper shielding by d and f electrons leads to irregularities in certain properties of elements.
- For example, it affects atomic radii and ionization enthalpies.

5. **Specific Properties Affected**:
- The irregularities can be observed in the atomic radii and ionization enthalpy of d-block and f-block elements, as well as in group 13 elements.

### Summary
- The d and f orbital electrons are known for their improper shielding of the nuclear charge due to their scattered structure. This results in irregularities in properties such as atomic radii and ionization enthalpy for certain elements.