21.5 Color and Paramagnetism of Complex Ions and Coordination Compounds | General Chemistry

Chad provides a succinct lesson explaining why many coordination compounds are vividly colored and explains how to determine if a complex will be paramagnetic or diamagnetic. The crystal field splitting energy corresponds to the energy of the light absorbed by many transition metal complexes as an electron is promoted from lower energy d orbital to a higher energy d orbital. It also commonly corresponds to the energy of visible light. And if a complex absorbs visible light, it will typically appear to have the complementary color in appearance. Finally, a steadfast rule is provided allowing one to determine which transition metal complexes should be expected to be colored and which to be colorless.

A paramagnetic complex experiences a weak attractive force when moving through a magnetic field resulting from a net spin due to the presence of unpaired electrons. So if a transition metal in a complex has unpaired electrons it will be paramagnetic. But if all the electrons are paired up there is no net spin and the species will experience a very, very slight repulsion in a magnetic field and is said to be diamagnetic. Chad reviews how to fill in the d electrons based upon the type of coordination complex (octahedral/low spin, octahedral/high spin, tetrahedral, or square planar) to determine if and how many unpaired electrons may be present.

I've embedded this playlist as a course on my website with all the lessons organized by chapter in a collapsible menu and much of the content from the study guide included on the page. Check this lesson out at https://www.chadsprep.com/chads-gener...

If you want all my study guides, quizzes, final exam reviews, and practice exams, check out my General Chemistry Master Course (free trial available) at https://www.chadsprep.com/genchem-you...

00:00 Lesson Introduction
00:26 Color of Transition Metal Complexes
06:53 Paramagnetic vs Diamagnetic
09:17 Sc^3+: Colorless and Diamagnetic
10:32 Cu^+: Colorless and Diamagnetic
12:06 Fe^2+ (low spin): : Colored and Diamagnetic
14:30 Fe^2+ (high spin): Colored and Paramagnetic
15:53 Cr^3+: Colored and Paramagnetic
17:21 FeF6^3- (weak field): Colored and Paramagnetic
19:19 Ni^2+ (square planar): Colored and Diamagnetic
20:12 Spectrochemical Series

https://www.chadsprep.com/
https://courses.chadsprep.com/pages/p...