Bohr Model and Electron Transitions: Absorption and Emission

Atoms and Elements

Bohr Model (Simplified)

The Bohr Model describes electrons traveling around the nucleus in circular orbits called shells. Each shell represents a grouping of electrons with a specific potential energy level.

• Shell (n): The principal quantum number (n) indicates the shell or energy level of an electron.

• Potential Energy: The energy an object possesses based on its position. In atoms, electrons in shells further from the nucleus have higher potential energy.

Diagram: The Bohr Model shows concentric circles around the nucleus, each representing a shell (n = 1, 2, 3, ...).

• n = 1: Closest shell to the nucleus (lowest energy)

• n = 2, 3, ...: Successively farther shells (higher energy)

Example: For an atom with electrons in shells n = 1, 2, 3, 4, 5, 6, the electron furthest from the nucleus is in shell n = 6.

Electrons in Atoms and the Periodic Table

Absorption and Emission

Electrons can move between shells by absorbing or emitting energy. These transitions are fundamental to understanding atomic spectra and chemical behavior.

• Absorption: When an electron absorbs energy, it moves from a lower shell to a higher shell (farther from the nucleus).

• Emission: When an electron emits energy, it moves from a higher shell to a lower shell (closer to the nucleus).

Key Points:

• Energy is absorbed when electrons move to shells with higher n (e.g., n = 2 to n = 5).

• Energy is emitted when electrons move to shells with lower n (e.g., n = 4 to n = 1).

• The greater the difference between shells, the more energy is absorbed or emitted.

Diagram: Absorption and emission are illustrated by arrows showing electron movement between shells.

Practice Questions (with Academic Context)

• Which electron transition represents absorption?

  • Absorption occurs when an electron moves to a higher shell (e.g., n = 1 to n = 3).

• Which electron transition represents emission?

  • Emission occurs when an electron moves to a lower shell (e.g., n = 3 to n = 1).

• Which electron transition represents absorption with the greatest energy?

  • The largest jump between shells (e.g., n = 1 to n = 6) involves the greatest energy absorption.

Equations and Formulas

• Energy of Electron Transition: $E = -R_H \left( \frac{1}{n_f^2} - \frac{1}{n_i^2} \right)$ Where $E$ is the energy change, $R_H$ is the Rydberg constant, $n_i$ is the initial shell, and $n_f$ is the final shell.

• Absorption: $n_i < n_f$ (energy absorbed)

• Emission: $n_i > n_f$ (energy emitted)

Summary Table: Electron Transitions

Type of Transition	Direction	Energy Change	Example
Absorption	Lower n to higher n	Energy absorbed	n = 2 to n = 5
Emission	Higher n to lower n	Energy emitted	n = 4 to n = 1

Additional info: The Bohr Model is a simplified representation and is most accurate for hydrogen-like atoms. Modern quantum mechanics provides a more complete description, but the Bohr Model remains useful for understanding basic electron transitions and atomic spectra.