(a) The average distance from the nucleus of a 3s electron in a chlorine atom is smaller than that for a 3p electron. In light of this fact, which orbital is higher in energy?

Verified step by step guidance

1. Understand the concept of orbital energy levels: In an atom, electrons occupy orbitals, and these orbitals have different energy levels. The energy of an orbital is influenced by its shape and the average distance of the electron from the nucleus.
2. Recognize the relationship between distance and energy: Electrons that are closer to the nucleus are generally lower in energy due to the stronger electrostatic attraction between the negatively charged electron and the positively charged nucleus.
3. Compare the 3s and 3p orbitals: The problem states that the average distance from the nucleus of a 3s electron is smaller than that for a 3p electron. This implies that the 3s electron is closer to the nucleus compared to the 3p electron.
4. Determine which orbital is higher in energy: Since the 3s electron is closer to the nucleus, it experiences a stronger attraction and is therefore lower in energy compared to the 3p electron, which is further away.
5. Conclude that the 3p orbital is higher in energy: Based on the above analysis, the 3p orbital is higher in energy than the 3s orbital because the 3p electron is on average further from the nucleus.

Key Concepts

Electron Orbitals

Electron orbitals are regions around an atom's nucleus where electrons are likely to be found. They are defined by quantum numbers and have distinct shapes and energy levels. The 3s and 3p orbitals are both in the third energy level, but they differ in shape and energy, with s orbitals being spherical and p orbitals having a dumbbell shape.

Energy Levels and Electron Configuration

In an atom, electrons occupy energy levels based on their distance from the nucleus and the type of orbital. Generally, p orbitals are higher in energy than s orbitals within the same principal energy level due to increased electron-electron repulsion and the shape of the orbitals, which affects their spatial distribution around the nucleus.

Effective Nuclear Charge

Effective nuclear charge (Z_eff) refers to the net positive charge experienced by an electron in a multi-electron atom. It accounts for the shielding effect of inner electrons. In the case of chlorine, the 3p electrons experience a lower effective nuclear charge compared to 3s electrons, contributing to their higher energy state due to less attraction to the nucleus.