UNIT OVERVIEW

Everything around you is made of atoms. The air you breathe, the water you drink, the phone in your hand—all are built from tiny particles called atoms. But what is inside an atom? How did scientists discover what they could not see?

In this unit, you will learn how our understanding of atoms developed over time. You will discover what makes up an atom, how to calculate atomic mass, and why electrons arrange themselves in specific patterns.

By the end of this unit, you will be able to:

• Describe how atomic models developed from Dalton to the quantum mechanical model
• Explain the structure of an atom, including protons, neutrons, and electrons
• Calculate atomic mass and understand atomic size
• Define isotopes and calculate relative atomic mass
• Understand energy quantisation and electron energy levels
• Write electron configurations using the aufbau principle, Pauli exclusion principle, and Hund's rule
• Connect electron configuration to an element's position on the periodic table

Why does this matter?

• Medical imaging: Radioactive isotopes help doctors see inside your body without surgery
• Nuclear power: Koeberg Power Station near Cape Town uses uranium atoms to generate electricity
• Technology: The electron arrangement in silicon atoms makes your phone's processor work
• Archaeology: Carbon-14 dating helps scientists determine the age of artifacts from sites like Mapungubwe

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