The Periodic Table and properties of elements

The Periodic Table is a fundamental tool in chemistry that organises all known elements by increasing atomic number. In WJEC GCSE Combined Science, you need to understand how the table is arranged into periods (rows) and groups (columns), and how this arrangement reflects the electronic structure of atoms. Elements in the same group have the same number of outer electrons, which gives them similar chemical properties. This topic also covers the properties of metals and non-metals, and how elements are classified as metals, non-metals, or metalloids based on their position.

Understanding the Periodic Table is essential because it allows you to predict how elements will react and what compounds they will form. For example, Group 1 elements (alkali metals) are highly reactive and form +1 ions, while Group 7 elements (halogens) are reactive non-metals that form -1 ions. You will also learn about trends across periods, such as how atomic radius decreases and ionisation energy increases as you move from left to right. These patterns are linked to the number of protons and the arrangement of electrons in shells.

This topic builds on your knowledge of atomic structure and electron configuration. It is also a foundation for later topics like chemical bonding, reactivity series, and electrolysis. By mastering the Periodic Table, you will be able to explain why elements behave the way they do and make predictions about their properties. In the exam, you may be asked to interpret the table, describe trends, or use it to deduce the properties of an unfamiliar element.