Questions: Discuss the model of triads in the development of the periodic table and indicate how it contributed to the periodic table we are using today. [10]

Solution Steps

The concept of triads was introduced by Johann Wolfgang Döbereiner in the early 19th century. A triad is a group of three elements with similar chemical properties, where the atomic weight of the middle element is approximately the average of the other two. This was one of the earliest attempts to classify elements based on their properties and atomic weights.

Döbereiner identified several triads, such as chlorine, bromine, and iodine; calcium, strontium, and barium; and sulfur, selenium, and tellurium. These groups demonstrated a pattern where the properties of the middle element were intermediate between the other two, suggesting a relationship between atomic weight and chemical properties.

The model of triads was significant because it was one of the first systematic approaches to organizing elements based on their properties. It laid the groundwork for the development of the periodic table by highlighting the periodicity in element properties. This concept of periodicity was later expanded by Dmitri Mendeleev, who arranged elements in a table according to increasing atomic weight, leading to the modern periodic table.

Final Answer