As the nuclear charge increases from neon to calcium, the orbital energies

Options

A. Increase
B. Increases very rapidly
C. increases very slowly
D. Fall

Answer

To solve the question regarding the behavior of orbital energies as the nuclear charge increases from neon to calcium, we can follow these steps:

### Step 1: Understanding Nuclear Charge
- Nuclear charge refers to the total charge of the nucleus, which is determined by the number of protons present. As we move from neon (atomic number 10) to calcium (atomic number 20), the nuclear charge increases due to the addition of more protons.

### Step 2: Identifying the Electron Configuration
- Neon has the electron configuration of 1s² 2s² 2p⁶. When we move to calcium, the electron configuration becomes 1s² 2s² 2p⁶ 3s² 3p⁶ 4s². The key point here is that after filling the 3p orbital, the next electrons enter the 4s orbital.

### Step 3: Comparing Orbital Energies
- The 4s orbital is lower in energy than the 3d orbital. This means that as we add electrons to the 4s orbital after neon, the energy of the orbitals does not increase significantly. Instead, we can say that the energy of the orbitals falls or remains relatively stable compared to the increase in nuclear charge.

### Step 4: Conclusion
- Therefore, as the nuclear charge increases from neon to calcium, the orbital energies actually fall. The correct answer to the question is that the orbital energies "fall."

### Final Answer
- The correct option is D: "fall."

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