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 valence electron experiences the maximum effective nuclear charge, we need to consider the concepts of effective nuclear charge, shielding effect, and the relative distances of the electrons from the nucleus.

### Step-by-Step Solution:

1. **Understanding Effective Nuclear Charge (Z_eff)**:
- Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the actual nuclear charge (number of protons) minus the shielding effect of inner-shell electrons.

**Hint**: Remember that Z_eff = Z - S, where Z is the actual nuclear charge and S is the shielding constant.

2. **Identifying the Shells and Orbitals**:
- Electrons are arranged in shells (n) and subshells (s, p, d, f). The effective nuclear charge experienced by an electron depends on its distance from the nucleus and the shielding effect from other electrons.
- The order of penetration of orbitals is: s > p > d > f. This means s orbitals penetrate closer to the nucleus than p, d, and f orbitals.

**Hint**: Recall that the closer an electron is to the nucleus, the stronger the effective nuclear charge it experiences.

3. **Comparing Different Orbitals**:
- When comparing orbitals from different shells, electrons in lower principal quantum number shells (n) will experience a stronger effective nuclear charge due to less shielding.
- For example, electrons in the 2p orbital will experience more effective nuclear charge than those in the 3s or 3p orbitals because they are closer to the nucleus.

**Hint**: Focus on the principal quantum number (n) and the type of orbital (s, p, d, f) to determine which electrons are closest to the nucleus.

4. **Evaluating the Options**:
- If we consider the options provided (not specified in the question), we would analyze the effective nuclear charge for each valence electron based on its shell and subshell.
- For instance, if the options include 2p, 3s, 3p, and 4s, the 2p electrons would experience the maximum effective nuclear charge because they are in the second shell, which is closer to the nucleus compared to the others.

**Hint**: Compare the principal quantum numbers and the types of orbitals to find the one that is closest to the nucleus.

5. **Conclusion**:
- Based on the above analysis, the valence electron that experiences the maximum effective nuclear charge is the one in the 2p orbital, as it is closest to the nucleus and experiences the least shielding from other electrons.

**Final Answer**: The valence electron in the 2p orbital experiences the maximum effective nuclear charge.