Aufbau Principle Examples: Determining Electron Configuration

📚 Quick Study Guide

• ⚛️ The Aufbau principle states that electrons first fill the lowest energy levels available.
• 📈 The order of filling orbitals is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.
• 📐 Hund's rule states that within a subshell, electrons individually occupy each orbital before any orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.
• 🔑 Pauli Exclusion Principle: No two electrons in the same atom can have the same set of quantum numbers. Therefore, each orbital can hold a maximum of two electrons, with opposite spins.
• 🧪 Remember: s orbitals hold up to 2 electrons, p orbitals hold up to 6 electrons, d orbitals hold up to 10 electrons, and f orbitals hold up to 14 electrons.
• 📝 Shorthand Notation: Use the previous noble gas to shorten electron configurations, e.g., Sodium (Na) is $[Ne]3s^1$.

Practice Quiz

1. What is the electron configuration of Potassium (K)?
   1. $1s^22s^22p^63s^23p^6$
   2. $1s^22s^22p^63s^23p^64s^2$
   3. $1s^22s^22p^63s^23p^64s^1$
   4. $1s^22s^22p^63s^23p^54s^2$
2. According to the Aufbau principle, which orbital is filled immediately after the 3p orbital?
   1. 3d
   2. 4s
   3. 4p
   4. 5s
3. What is the maximum number of electrons that can occupy a p subshell?
   1. 2
   2. 6
   3. 10
   4. 14
4. What is the shorthand electron configuration for Iron (Fe)?
   1. $[Ar]4s^23d^4$
   2. $[Ar]4s^23d^6$
   3. $[Kr]4s^23d^6$
   4. $[Ar]4s^24d^6$
5. Which of the following elements has the electron configuration $1s^22s^22p^3$?
   1. Carbon (C)
   2. Nitrogen (N)
   3. Oxygen (O)
   4. Fluorine (F)
6. Which rule states that electrons individually occupy each orbital within a subshell before any orbital is doubly occupied?
   1. Aufbau Principle
   2. Pauli Exclusion Principle
   3. Hund's Rule
   4. Heisenberg Uncertainty Principle
7. What is the electron configuration of $Cu^{2+}$ (Copper (II) ion)?
   1. $[Ar]4s^13d^8$
   2. $[Ar]4s^23d^7$
   3. $[Ar]3d^9$
   4. $[Ar]4s^13d^{10}$