Atomic Structure and Periodicity of Elements - Chemistry (Undergraduate Foundation)

This course provides a complete guide to the modern theory of the atom. It traces the historical development of atomic models, from Dalton's foundational theory to the modern understanding of electronic structure. The material covers the discovery of subatomic particles, the contributions of Thomson and Rutherford, the Bohr model, and culminates in a full treatment of electronic configuration and its direct relationship to the periodic trends of the elements. A command of atomic theory is the absolute foundation of modern chemistry. The electronic structure of the atom dictates all chemical properties and bonding behaviour. This knowledge is essential for understanding the periodic table, predicting chemical reactions, and is the prerequisite for the study of spectroscopy, materials science, and quantum mechanics. By the end of this course, you will be able to describe the historical evolution of atomic theory. You will also be able to explain the structure of the atom, including the roles of protons, neutrons, and electrons, determine the electronic configuration of any element, and use periodic trends to predict and justify atomic properties like size, ionization potential, and electronegativity. This course is for students who have completed an introductory chemistry course. It is a mandatory prerequisite for any student pursuing a degree in chemistry, chemical engineering, materials science, or physics.

Payment required for enrolment

Enrolment valid for 12 months

This course is also part of the following learning track. You may join the track to gain comprehensive knowledge across related courses.

[NUC Core] CHM 101: General Chemistry I

This learning track delivers the complete NUC CCMAS curriculum for General Chemistry I. It is a comprehensive programme designed to build a robust, university-level foundation in modern chemistry. The track systematically covers all essential topics, from atomic theory, chemical bonding, and the states of matter, to the quantitative principles of stoichiometry, equilibrium, thermodynamics, and kinetics. This programme is for first-year undergraduates in science, technology, engineering, and mathematics (STEM) faculties who are required to take CHM 101. It is also essential for any student or professional globally who needs a rigorous and complete foundation in first-year university chemistry for further study or career development. This track delivers a full skill set in chemical theory and quantitative problem-solving. Graduates will be able to determine molecular structures, calculate reaction quantities, analyse the energetics and rates of reactions, and solve complex equilibrium problems. This programme provides the non-negotiable prerequisite knowledge for all subsequent chemistry courses and for any degree in the physical sciences, engineering, or medicine.

Course Chapters

1. Introduction

This chapter provides the roadmap for the course. It outlines the progression from early atomic theories to the modern understanding of atomic structure and its direct relationship to the periodic table. Key learning objectives include: understanding the overall course structure and appreciating the historical and experimental development of atomic theory.

Chapter lessons

1-1. Welcome

6:35

This lesson provides a brief overview of the course, outlining the key topics from Dalton's postulates to electronic configuration and periodic trends.

2. Early Atomic Models

This chapter covers the foundational postulates of modern chemistry. It focuses on Dalton's atomic theory and the initial discoveries that showed the atom was divisible. Key learning objectives include: outlining the postulates of Dalton's atomic theory; and describing the evidence for the divisibility of the atom from the discovery of the electron.

Chapter lessons

2-1. Laws of chemical combination

11:05

This lesson examines the laws governing mass relationships in chemical reactions. We cover conservation of mass, definite proportions, and multiple proportions. Understand these principles as the quantitative evidence for Dalton's atomic theory.

2-2. Dalton's atomic theory

This lesson covers the four fundamental postulates of John Dalton's atomic theory, which established the first scientific model of the atom.

2-3. Shortcomings of Dalton's atomic theory

Dalton's theory was foundational but flawed. This lesson identifies its critical shortcomings, namely the divisibility of atoms and the existence of isotopes. Understanding these failures is necessary to trace the progression to modern atomic models.

2-4. Thomson's cathode ray experiment

This lesson details J.J. Thomson's cathode ray experiment. The experiment provides the definitive evidence for the electron and allows for the calculation of its charge-to-mass ratio. This discovery proved the atom is divisible, refuting a key part of Dalton's theory.

2-5. Milikan's Oil drop experiment

This lesson details Millikan's Oil drop experiment, which established the elementary electric charge. By using Thomson's charge-to-mass ratio, this experiment allowed for the first accurate calculation of the electron's mass.

3. The Nuclear Model

This chapter details the discovery of the atomic nucleus and the first quantum model of the atom. It covers the key experiments that established the modern planetary view of atomic structure. Key learning objectives include: explaining the contributions of Rutherford's gold foil experiment; and describing the Bohr model of the atom with its quantized energy levels.

Chapter lessons

3-1. Discovery of nucleus

This lesson details Rutherford's gold foil experiment and how its results led to the discovery of a small, dense, positively charged nucleus.

3-2. The Bohr model

This lesson introduces the Bohr model of the atom, which proposed that electrons orbit the nucleus in discrete, quantized energy levels, explaining atomic emission spectra.

4. The Quantum Model

This chapter covers the modern understanding of how electrons are arranged within an atom. It details the principles of electronic energy levels and explains how this structure gives rise to the periodic table. Key learning objectives include: defining electronic energy levels, sublevels, and orbitals; and determining the electronic configuration of any element using the standard filling rules.

Chapter lessons

4-1. Levels and orbitals

This lesson details the modern quantum mechanical model, defining the principal energy levels, sublevels (s, p, d, f), and orbitals that describe probable electron locations.

4-2. Aufbau and Pauli principles

This lesson introduces the Aufbau principle for filling orbitals and the Pauli exclusion principle, which governs the spin of electrons in an orbital.

4-3. Hund's rule

This lesson is dedicated to Hund's rule of maximum multiplicity, which explains how electrons are arranged in orbitals of the same sublevel.

5. Periodicity

This chapter explains how the electronic structure of atoms leads to predictable, periodic trends in their properties across the periodic table. The focus is on justifying these trends based on concepts like shielding and effective nuclear charge. Key learning objectives include: defining and explaining the trends in atomic radii, ionization energies, and electronegativity across a period and down a group.

Chapter lessons

5-1. Atomic radii

This lesson defines atomic radius and explains the trend of decreasing size across a period and increasing size down a group.

5-2. Ionization energies

This lesson defines first ionization energy and explains the trend of increasing energy across a period and decreasing energy down a group.

5-3. Electronegativity

This lesson defines electronegativity as the ability of an atom to attract electrons in a chemical bond and explains its periodic trends.

6. Conclusion

This concluding chapter summarises the key concepts of atomic theory. It reinforces the understanding of atomic structure and its connection to the periodic properties of the elements. This summary prepares the student for the next course, 'Chemical Bonding and Molecular Geometry', where electronic structure is used to predict how atoms form molecules.

Chapter lessons

6-1. Course summary

This lesson consolidates knowledge by reviewing the progression from early atomic models to the modern understanding of electronic structure and periodic trends.

6-2. Next steps

This final lesson looks ahead, explaining how the principles of electronic configuration and periodicity are the direct prerequisites for understanding chemical bonding.