Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

Which scientist discovered that electrons move around the nucleus in defined orbits?

1. Max Planck

2. Niels Bohr

3. Louis de Broglie

4. Werner Heisenberg

The correct answer is: Niels Bohr

The discovery that electrons move around the nucleus in defined orbits is attributed to Niels Bohr. Bohr proposed his model of the atom in 1913, introducing the idea that electrons exist in specific energy levels or orbits around the nucleus, akin to planets orbiting the sun. This was a significant development in atomic theory, as it offered a more structured understanding of electron behavior compared to earlier models. Bohr's model addressed how electrons could occupy these stable orbits without radiating energy, which was a key issue in classical physics. Additionally, he introduced the concept of quantized energy levels, stating that electrons could only move between these defined orbits by absorbing or emitting energy in discrete amounts, or quanta. This quantization of electron orbitals was a foundational aspect of quantum mechanics and has had lasting implications in the field of physics. The other scientists listed contributed significantly to the understanding of atomic and subatomic processes but did not specifically focus on the concept of electrons moving in defined orbits around the nucleus. Max Planck's work laid the groundwork for quantum theory with his introduction of quantization of energy, while Louis de Broglie contributed the wave-particle duality concept, and Werner Heisenberg is known for his uncertainty principle