Nuclear charge actually experienced by an electron is termed as effective nuclear charge. The effective nuclear charge `Z^(**)` actuall ydepends on type of shell and orbital in which electron is actually present. The relative extent to which the various orbitals penetrate the electron clouds of other orbitals is
`s gt p gt d gt f` (for the same value of n)
The phenomenon in which penultimate shell electrons act as screen or sheild in between nucleus and valence shell electrons and thereby reducing nuclear charge is known as shielding effect. the penultimate shell electrons repel the valence shell electron to keep them loosely held with nucleus. it is thus evident that more is the shielding effect, lesser is the effective nuclear charge and lesser is the ionization energy.
Q. Which of the following valence electron experience maximum effective nuclear charge?

Options

A. `4s^(1)`
B. `4p^(1)`
C. `3d^(1)`
D. `2p^(3)`

Explanation

To determine which of the following valence electrons experiences the maximum effective nuclear charge, we need to analyze the given options based on the concepts of effective nuclear charge, shielding effect, and orbital penetration.

### Step-by-Step Solution:

1. **Understanding Effective Nuclear Charge (Z_eff)**:
- The effective nuclear charge is the net positive charge experienced by an electron in an atom. It is influenced by the actual nuclear charge (Z) and the shielding effect from other electrons.

2. **Factors Affecting Effective Nuclear Charge**:
- **Shell**: Electrons in shells closer to the nucleus experience a higher effective nuclear charge because they are less shielded by other electrons.
- **Orbital Type**: The penetration power of orbitals affects how much they shield each other. The order of penetration is:
- s > p > d > f (for the same principal quantum number n).

3. **Analyzing the Given Options**:
- **4s**: n = 4, in the fourth shell.
- **4p**: n = 4, in the fourth shell but has less penetration than 4s.
- **3d**: n = 3, in the third shell, experiences more shielding from the 4s and 4p electrons.
- **2p**: n = 2, in the second shell, experiences the least shielding and has the highest penetration.

4. **Conclusion**:
- Among the given options, the **2p** electrons experience the maximum effective nuclear charge because they are in the second shell and are less shielded compared to the other options, which are in higher shells and experience greater shielding.

### Final Answer:
The valence electrons that experience maximum effective nuclear charge are **2p** electrons.

---