This guide provides answers and explanations for a typical electron configuration worksheet, focusing on understanding the principles behind electron placement and the nuances of orbital filling. We'll cover common questions, tackle tricky scenarios, and help solidify your understanding of electron configurations. Remember that while this guide offers solutions, the true learning comes from understanding why these configurations are correct.
Understanding Electron Configuration
Before diving into the answers, let's quickly review the fundamental principles:
- Aufbau Principle: Electrons fill orbitals starting with the lowest energy levels.
- Pauli Exclusion Principle: Each orbital can hold a maximum of two electrons with opposite spins.
- Hund's Rule: Electrons fill orbitals individually before pairing up. This minimizes electron-electron repulsion.
These three rules are crucial for correctly determining electron configurations. Let's apply them to examples.
Common Worksheet Questions & Answers
While specific worksheet questions vary, common themes emerge. Here's a breakdown addressing typical problem types:
1. Writing Electron Configurations for Neutral Atoms
Example: Write the electron configuration for Oxygen (O, atomic number 8).
Answer: 1s²2s²2p⁴
Explanation: Oxygen has 8 electrons. Following the Aufbau principle, we fill the orbitals in increasing energy order:
- 1s orbital holds 2 electrons (1s²)
- 2s orbital holds 2 electrons (2s²)
- 2p orbital holds 4 electrons (2p⁴) – remember, the 2p subshell has three orbitals (2px, 2py, 2pz), each holding a maximum of two electrons. Hund's rule dictates that the electrons fill these orbitals individually before pairing.
2. Noble Gas Configurations
Example: Write the noble gas configuration for Iron (Fe, atomic number 26).
Answer: [Ar] 3d⁶4s²
Explanation: Instead of writing the full configuration (1s²2s²2p⁶3s²3p⁶3d⁶4s²), we can use the noble gas notation. Argon (Ar) has an electron configuration of 1s²2s²2p⁶3s²3p⁶. Iron has 26 electrons, so we start with Argon's configuration and add the remaining electrons: 3d⁶4s².
3. Identifying Valence Electrons
Example: How many valence electrons does Sulfur (S, atomic number 16) have?
Answer: 6
Explanation: Sulfur's electron configuration is [Ne]3s²3p⁴. Valence electrons are the electrons in the outermost shell (highest principal quantum number). In this case, the outermost shell is the third shell (n=3), which contains 6 electrons (2 from 3s and 4 from 3p).
4. Electron Configurations of Ions
Example: What is the electron configuration of the O²⁻ ion?
Answer: 1s²2s²2p⁶
Explanation: Oxygen gains two electrons to become a 2- anion, filling its 2p subshell. This results in a stable noble gas configuration (like Neon).
5. Determining the Element from the Electron Configuration
Example: Identify the element with the electron configuration [Kr]5s²4d¹⁰5p².
Answer: Tin (Sn)
Explanation: Count the total number of electrons (36 from Krypton + 2 + 10 + 2 = 50). The atomic number 50 corresponds to Tin on the periodic table.
Tips for Success
- Practice: The best way to master electron configurations is through consistent practice. Work through numerous examples, gradually increasing the complexity.
- Periodic Table: Use the periodic table as a guide. The arrangement of elements reflects their electron configurations.
- Visual Aids: Diagrams illustrating orbital filling can be extremely helpful in visualizing the process.
This guide provides a solid foundation for understanding and solving electron configuration problems. Remember, consistent practice and a clear understanding of the underlying principles are key to success. If you have further questions or specific worksheet problems you'd like assistance with, feel free to ask!
