Then and Now – The Periodic Table Element – Potassium. Potassium, with its atomic symbol K and atomic number 19, is a highly reactive element found abundantly in nature. Throughout history, it has played a pivotal role in various human activities, including industrial processes, healthcare, and even warfare. However, due to its limitations and the emergence of alternative substances, potassium’s early applications have largely become obsolete. This article explores the first uses of potassium, shedding light on why it is no longer favored for those purposes. Read more.