KONFIGURASI ELEKTRON BERDASARKAN TEORI ATOM MEKANIKA KUANTUM

Introduction

This tutorial provides a step-by-step guide on determining electron configurations based on quantum mechanical atomic theory. Understanding electron configurations is essential for grasping the behavior of atoms in chemistry, including their reactivity and bonding patterns.

Step 1: Understand Quantum Numbers

Quantum numbers are essential for defining the properties of atomic orbitals, including:

• Principal Quantum Number (n): Indicates the energy level and size of the orbital. Values are positive integers (1, 2, 3…).
• Azimuthal Quantum Number (l): Defines the shape of the orbital. Values range from 0 to (n-1).
• Magnetic Quantum Number (m_l): Specifies the orientation of the orbital in space. Values range from -l to +l.
• Spin Quantum Number (m_s): Indicates the spin direction of the electron, with values of +1/2 or -1/2.

Practical Tip

Familiarize yourself with the significance of each quantum number to understand how they influence electron arrangement.

Step 2: Follow the Aufbau Principle

The Aufbau Principle states that electrons fill orbitals starting from the lowest energy level to the highest. The order of filling is generally:

1. 1s
2. 2s
3. 2p
4. 3s
5. 3p
6. 4s
7. 3d
8. 4p
9. 5s
10. 4d
11. 5p
12. 6s
13. 4f
14. 5d
15. 6p
16. 7s
17. 5f
18. 6d
19. 7p

Common Pitfall

Do not skip orbitals; always fill lower energy levels first before moving to higher ones.

Step 3: Apply the Pauli Exclusion Principle

The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers. This means:

• Each orbital can hold a maximum of two electrons with opposite spins.

Practical Tip

When writing configurations, indicate spins (↑ and ↓) to demonstrate how electrons are paired in orbitals.

Step 4: Utilize Hund's Rule

Hund's Rule states that electrons will occupy degenerate orbitals (orbitals of the same energy) singly before pairing up. This helps minimize the repulsion between electrons.

Example

For the 2p orbital, the filling order would be:

• 2p: ↑ ↑ ↑ (then pair if necessary)

Step 5: Write Electron Configuration

To write the electron configuration:

1. Start from the lowest energy level.
2. Fill each orbital according to the principles outlined above.
3. Use superscripts to indicate the number of electrons in each orbital.

Example

For Phosphorus (atomic number 15):

• Configuration: 1s² 2s² 2p⁶ 3s² 3p³

Conclusion

Understanding electron configurations is fundamental in chemistry. By mastering quantum numbers, the Aufbau principle, the Pauli exclusion principle, and Hund's rule, you can accurately determine how electrons are arranged in an atom. This knowledge is crucial for predicting chemical behavior and bonding. As next steps, consider exploring related topics such as valence electrons and their role in chemical reactions.