Intermediate Chemistry: Periodicity and Periodic Table

Dmitri Mendeleev arranged elements by atomic mass (the sum of protons and neutrons) and the modern Periodic Table orders them by atomic number (the number of protons or electrons in a neutral atom). We begin by identifying the eighteen ‘groups’ (vertical columns) and seven ‘periods’ (horizontal rows) found in today's Periodic Table. We study four (‘s’, ‘p’, ‘d’ and ‘f’) block elements, their location in the Periodic Table and their subshells filling. We then examine the placement of metals, metalloids and non-metals and their properties.

The course then delves into the periodicity of physical properties, beginning with atomic radii. We then explain how melting points and conductivity across periods are affected by the type of element and formed bonds. For example, metals have high melting points because they form powerful metallic bonds while non-metals have lower melting points because they make up simple molecules. Our next topic describes how a higher electronegativity in period 3 increases the first ionisation energy of non-metals relative to metals.

We trace the effect of changes in valence electrons on various chemical properties across the Periodic Table. We outline how period 3 elements like sodium, magnesium and sulphur react with hydrogen and produce golden yellow, bright and blue flames while forming oxides. We demonstrate how quickly or slowly metals, non-metals and metalloids react with chlorine to form chlorides. Finally, we explain how some period 3 chlorides, such as sodium and magnesium, dissociate in water into ions while others, like silicon and phosphorus, hydrolyse and emit white fumes. This course has no prerequisites and is designed for anyone who wants to improve their chemistry skills. Sign up to explore the building blocks of matter and learn how to arrange elements on the Periodic Table.