Investigating the Periodic Table with Experiments - with Peter Wothers

The speaker begins by expressing excitement about the International Year of the Periodic Table, marking the 150th anniversary of its publication. The periodic table organizes the 118 known elements, highlighting their properties and relationships. The speaker references the original periodic table by Dimitri Mendeleev, published in 1869, and notes its differences from modern versions. The speaker also mentions an upcoming exhibition at the Royal Society of Chemists in London, where various versions of the periodic table will be displayed, including Mendeleev's original and a unique cylindrical version. The importance of understanding the structure of atoms to comprehend the periodic table is emphasized, leading into a discussion about the basic components of atoms: protons, neutrons, and electrons.

The speaker delves into the structure of the periodic table, explaining how elements are arranged by increasing atomic number, which corresponds to the number of protons in an atom's nucleus. The speaker describes the significance of grouping elements with similar chemical properties into vertical columns, known as groups or families. The lecture highlights the properties of group 1 elements, which all have one electron in their outermost shell, leading to similar chemical behaviors. The speaker also touches on the instability of heavier elements and their tendency towards radioactive decay, using the example of francium. The discussion then moves to group 2 elements, which have two outermost electrons, setting the stage for further exploration of the periodic table's patterns.

The speaker focuses on the halogen group (group 17), known for their high reactivity and ability to form salts. The halogens, including fluorine, chlorine, bromine, iodine, and astatine, are detailed with anecdotes about their discovery and properties. The speaker performs a dramatic demonstration involving the explosion of nitrogen triiodide, showcasing the reactivity of iodine. The lecture also touches on the noble gases (group 18), highlighting their lack of reactivity and the historical significance of their discovery. The speaker emphasizes the unique properties of noble gases, such as helium's inertness and the individual atoms in a helium balloon.

The speaker compares the chemical properties of hydrogen and helium, demonstrating their distinct behaviors when reacting with oxygen. A lighted splint is used to identify the contents of two balloons, one filled with hydrogen and the other with helium. The hydrogen balloon explodes upon contact with the flame, illustrating its reactivity, while the helium balloon does not react and extinguishes the flame, demonstrating its inertness. The speaker also discusses the historical significance of hydrogen's discovery and its role in forming water when it combines with oxygen. The lecture concludes with a look at the work of early chemists like Lavoisier and the evolving understanding of elements and chemical reactions.

The speaker discusses the evolution of the list of elements and the understanding of chemical properties. Reference is made to the works of Lavoisier and Jane Marcet, whose books helped popularize chemistry and inspired scientists like Michael Faraday. The speaker describes the historical context in which certain substances, such as potash and soda, were considered elements due to their inability to be broken down further. The lecture also touches on the discovery of new elements like sodium and calcium by Humphry Davy and the subsequent updates to Marcet's list of elements. The speaker emphasizes the importance of classification systems in understanding and predicting the properties of elements, as seen in Mendeleev's periodic table.

The speaker explores how elements react with oxygen to form oxides, using magnesium as an example. Magnesium burns with a brilliant white light, forming magnesium oxide. The speaker also demonstrates the reaction of calcium with water, producing calcium hydroxide and hydrogen gas. The lecture delves into Mendeleev's predictions about the properties of undiscovered elements, such as ekaboron (scandium), and the accuracy of these predictions upon the element's discovery. The speaker then shows the burning of scandium, which forms scandium oxide, further illustrating Mendeleev's insights. The discussion highlights the relationship between an element's group and its oxide formation, emphasizing the predictive power of the periodic table.

The speaker discusses the thermite reaction, a high-temperature process involving aluminum and iron oxide to produce molten iron and aluminum oxide. The heat generated is so intense that it melts the iron. The lecture then explores the concept of bonding strengths and how they vary across the periodic table. The speaker uses carbon as an example, discussing its various forms (charcoal, graphite, diamond) and their properties, including diamond's exceptional hardness and heat conductivity. The demonstration shows how easily a diamond can cut through ice, highlighting its thermal conductivity. The speaker also touches on the density of elements and how it relates to the atomic structure and bonding, using tungsten and gold as examples of high density.

The speaker concludes the lecture with a final demonstration involving a hydrogen balloon. After a brief recap of the significance of hydrogen as the most abundant element in the universe, the speaker punctures the balloon, resulting in a popping sound without a loud explosion due to the absence of oxygen. The lecture ends on a high note, with the speaker expressing hope that the audience has enjoyed the informative and engaging presentation.