In which element the electrons will be experiencing the highest effective nuclear charge ? The elements are Be, B, C, N & O.

Options

A. O
B. Be
C. `Be ~~ B`
D. N= O

Answer

To determine which element has the highest effective nuclear charge (Z_eff) among Beryllium (Be), Boron (B), Carbon (C), Nitrogen (N), and Oxygen (O), we can follow these steps:

### Step 1: Understand Effective Nuclear Charge
Effective nuclear charge (Z_eff) is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the actual nuclear charge (the number of protons) and the shielding effect caused by other electrons.

### Step 2: Analyze the Elements
- **Beryllium (Be)**: Atomic number 4, has 4 protons and 4 electrons. The effective nuclear charge is relatively low due to the shielding effect of the inner electrons.
- **Boron (B)**: Atomic number 5, has 5 protons and 5 electrons. The effective nuclear charge increases slightly compared to Be.
- **Carbon (C)**: Atomic number 6, has 6 protons and 6 electrons. The effective nuclear charge continues to increase.
- **Nitrogen (N)**: Atomic number 7, has 7 protons and 7 electrons. The effective nuclear charge is higher than that of Carbon.
- **Oxygen (O)**: Atomic number 8, has 8 protons and 8 electrons. The effective nuclear charge is the highest among these elements.

### Step 3: Compare the Effective Nuclear Charge
As we move from left to right across the periodic table, the number of protons increases while the shielding effect does not increase significantly (since we are adding electrons to the same energy level). Therefore, the effective nuclear charge increases.

### Conclusion
Among the elements Be, B, C, N, and O, Oxygen (O) has the highest effective nuclear charge due to its higher number of protons compared to the others.

### Final Answer
**Oxygen (O)** experiences the highest effective nuclear charge among the given elements.

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