Chemistry I / Orbitals, Quantum Numbers and Electron Configuration
Practice question · Multiple choice

In a hydrogen atom the 2s2s and 2p2p orbitals have equal energy, but in lithium the 2s2s lies lower. Why?

Hints
  1. Hydrogen differs from every other atom in exactly one respect.
  2. With several electrons, shielding and repulsion make energy depend on l as well as n.
Show the answer

C. Electron-electron repulsion splits subshells once more than one electron is present

Why

Hydrogen has a single electron, so nothing breaks the degeneracy and energy depends on nn alone. Add a second electron and repulsion plus shielding make the more penetrating 2s2s lower than 2p2p.

Read the lesson: Orbitals, Quantum Numbers and Electron Configuration →

Practise Orbitals, Quantum Numbers and Electron Configuration

The app has 4 more questions on this lesson, and keeps your place in the course. Chemistry I is free to start.

More questions on Orbitals, Quantum Numbers and Electron Configuration