Overview
This lecture covers the electron configurations of transition metals, emphasizing how to write condensed configurations and handle exceptions and ions.
Electron Configuration Basics
- Electron configuration shows the distribution of electrons in atomic orbitals.
- The Aufbau principle dictates the order in which orbitals are filled (s, p, d, f).
- Notation includes principal quantum number (n), orbital type (s, p, d, f), and number of electrons.
- Condensed notation uses the previous noble gas in brackets, followed by remaining configuration.
Transition Metal Configurations
- Transition metals mainly fill s and d orbitals; f orbitals are involved in later periods.
- The d orbital holds up to 10 electrons (five shapes); f orbital holds up to 14 electrons (seven shapes); s holds up to 2 electrons (one shape).
- General d-block formula for periods 4-5: [Noble Gas] ns² (n-1)dˣ, x = 1–10.
- For periods 6-7: [Noble Gas] ns² (n-2)f¹⁴ (n-1)dˣ.
- Some elements (e.g., Cr, Mo, Cu, Ag) have exceptions for stability: ns¹ (n-1)d⁵ or ns¹ (n-1)d¹⁰.
Writing Configurations for Ions
- When forming ions, electrons are lost first from the ns orbital, then (n-1)d, then (n-2)f.
- For transition metal ions, remove s electrons before d electrons.
Example Problems
- Zr: [Kr] 5s² 4d²
- V³⁺: [Ar] 3d² (remove 3 electrons: 2 from 4s, 1 from 3d)
- Mo³⁺ (exception): [Kr] 4d³ (after removing electrons from 5s¹ 4d⁵)
- Re⁴⁺: [Xe] 4f¹⁴ 5d³ (remove 2 from 6s², 2 from 5d⁵)
Key Terms & Definitions
- Aufbau Principle — electrons fill the lowest energy orbitals first.
- Condensed Configuration — shorthand using noble gas core in brackets.
- Transition Metals — elements filling d orbitals, often periods 4–7.
- Exceptions — elements with electron configurations differing from the standard filling order for increased stability.
Action Items / Next Steps
- Practice writing electron configurations and their condensed forms for transition metals and ions.
- Create flashcards for key formulas and exceptions.
- Review periodic table placement for transition metals.