ASR Basic Principles of Spectroscopy Notes

2025 JC2 H3 Chemistry ©2025ASRJC/CHEM WE ARE ASR 1 Anderson Serangoon Junior College H3 Chemistry Basic Principles of Spectroscopy Lesson Outline Note: You should follow the sequence of content below. Skipping any pages will affect your understanding of later parts. All videos can be found in MS Teams Channel “Basic Principles of Spectroscopy”. Content Page Instructions for SDL lesson Relevant videos 1 Introduction 3 Self-read 2 Electromagnetic spectrum 3 - 5 Self-read 2.1 What is electromagnetic radiation? 2.2 Generation of light from atoms 2.3 Line emission spectra (quantisation of energy & energy level transitions) 3 Molecular Orbital (MO) Theory 3.1 Atomic Orbital 6 Self-read 3.2 Molecular Orbital 7 - Self-read - Watch Video 1 for elaboration 3.3 Linear Combination of Atomic Orbitals 7 - 8 3.4 HOMO and LUMO 9 3.5 Bond order 9 3.6 Homonuclear diatomic molecules 9 – 14 - Watch Video 2a_A Brief Introduction to Molecular Orbital Theory - Watch Video 2b_Summary 3.7 Conjugated and aromatic molecules 15 – 16 - Watch Video 3_Molecular Orbitals of Conjugated Alkenes 4 Self-check exercises 17 - 19 - Attempt all Self-check exercises. - Watch Video 4_Self-check Exercise 1 and 2 5 Additional readings 20 Self-read

2025 JC2 H3 Chemistry ©2025ASRJC/CHEM WE ARE ASR 2 H3 Chemistry Basic Principles Of Spectroscopy Learning outcomes Students should be able to: (a) understand basic Molecular Orbital (MO) theory, involving (i) atomic and molecular orbitals (ii) bonding, anti–bonding and non–bonding orbitals (iii) molecular orbitals with  and  symmetry (b) understand that molecular orbitals represent discrete electronic energy levels in molecules [see also (e)(ii)] (c) apply Linear Combination of Atomic Orbitals (LCAO) principles to obtain the shape and relative energ ies of molecular orbitals in the following: (i) simple homonuclear diatomic molecules such as H2, O2, and F2 (ii) benzene and linear polyenes (molecular orbitals of  symmetry only) [quantitative treatment of LCAO is not required] (d) construct and interpret molecular orbital diagrams, and identify the Highest Occupied Molecular Orbi tal (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) for the following: (i) simple homonuclear diatomic molecules such as H2, O2, and F2 (ii) benzene and linear polyenes (molecular orbitals of  symmetry only) [knowledge of orbital mixing between orbitals of the same symmetry is not required] (e) understand the following in relation to the fundamental principles of spectroscopy: (i) properties of electromagnetic radiation  the electromagnetic spectrum (with range of wavelengths for different types of radiation used in spectroscopy)  the photon as a discrete packet (quantum) of electromagnetic energy  the relationship between wavelength, frequency and speed of light, including the