Lesson 10: The Periodic Table

  1. Objectives
  2. Elements in Alchemy
    1. Classical Elements
    2. Metals in Alchemy
  3. The First Table
  4. Adding New Elements
  5. Mendeleev’s Table
  6. Marie Curie and Radioactivity
  7. Synthetic Elements
  8. Vocabulary List
  9. Vocabulary Practice
  10. Reflection Questions

Objectives

  1. Continuation of history of chemistry from Lesson 9
  2. Learn about the development and notation in the periodic table.

Elements in Alchemy

As we’ve seen in Lesson 9, the concept of elements in alchemy was fundamentally different from the modern understanding of chemical elements. Alchemists sought to understand the nature of matter and its transformations, often focusing on the idea of transmutation—the process of changing one substance into another, particularly the transformation of base metals into gold.

Classical Elements

In alchemical traditions, the classical elements consisted of four primary substances: earth, air, fire, and water. Each of these elements was associated with specific qualities: earth was cold and dry, air was hot and wet, fire was hot and dry, and water was cold and wet. This classification system allowed alchemists to categorize materials and understand their properties in relation to one another. The interplay between these elements was thought to influence not only physical substances but also human health and temperament, leading to a holistic view of the natural world.

Alchemists believed that by manipulating these elements through various processes—such as heating, cooling, and combining—they could create new substances or purify existing ones. The goal of these transformations was not just practical; it also had a spiritual dimension. Many alchemists viewed their work as a form of self-improvement, seeking to refine not only materials but also their own character and understanding of the universe.

The concept of a fifth element, known as “quintessence” or “aether,” was also integral to alchemical thought. Quintessence was believed to represent a perfect, divine substance that permeated the universe, connecting the celestial and terrestrial realms. Alchemists aimed to understand how these elements interacted and how they could be manipulated to achieve desired transformations. Although this understanding lacked empirical validation, it laid the groundwork for later scientific inquiry into the nature of matter and the elements.

Moreover, alchemical texts often included intricate diagrams and symbols to represent these elements and their interactions. These illustrations served both as a means of communication among practitioners and as a way to encode complex ideas about the nature of reality. The alchemical approach to elements emphasized not only their physical properties but also their symbolic meanings, which reflected the interconnectedness of matter, spirit, and the cosmos.

The interconnectedness of different parts of the human mind, of governments, and of the cosmos were all important concepts in Greek philosophy.

Metals in Alchemy

Metals held a special place in alchemical practices, often viewed as the most valuable and transformative substances. Alchemists believed that all metals were composed of a mixture of the classical elements, with specific metals corresponding to particular qualities. For instance, gold was considered the most perfect metal, symbolizing purity and perfection, while lead was associated with the base, impure state of matter.

Alchemical texts frequently included elaborate recipes and processes for metal transformation, which involved heating, distillation, and various chemical reactions. These practices, while mystical in nature, also laid the groundwork for practical metallurgy and the study of chemical reactions. Alchemists meticulously recorded their observations and experiments, often creating a rich body of knowledge that would later inform the scientific method.

The symbolic language of metals in alchemy also contributed to a broader understanding of the natural world. For example, the process of refining metals was often paralleled with personal transformation, illustrating the belief that spiritual and material growth were interconnected. Metals were also associated with heavenly bodies, with gold being assigned the Sun, and lead assigned Saturn (at then the farthest known planet from the Sun). Alchemy set a precedent for symbolic language, but it also connected science and philosophy by making it seem as though alchemists were embarking on a cosmic journey of purification and enlightenment.

The First Table

The quest to classify elements gained momentum in the late 18th and early 19th centuries as chemists sought to systematize the growing body of knowledge about known substances. In 1803, the English scientist John Dalton proposed an early table of atomic weights, marking the beginning of a more organized approach to understanding chemical elements. His atomic theory posited that each element is composed of unique atoms with specific weights, allowing for comparisons between different substances. This early framework provided a foundational structure for the burgeoning field of chemistry.

Dalton was also color-blind and is credited with the first systematic studies and research into color vision deficiencies. He initially believed that his color-blindness was due to discoloration in his eyes, which was later proven to be false.

Dalton’s work was pivotal, yet it lacked comprehensiveness, as many elements were not included in his atomic weight table. The understanding of atomic weights was still rudimentary, and as new elements were discovered, the need for a more systematic classification became apparent. Chemists began refining their definitions and methods for determining atomic weights, leading to significant developments in the field.

The limitations of Dalton’s table prompted further research and experimentation. Other scientists, such as Jöns Jacob Berzelius, contributed to the field by developing more accurate methods for measuring atomic weights and systematically categorizing elements. In 1813, Berzelius introduced a new system of chemical symbols, which enhanced communication among chemists and facilitated the recording of chemical reactions. Similar to how Linnaeus developed the genus-species shorthand for biological organisms, Berzelius reduced each known element to one or two letters: “O” for oxygen, “H” for hydrogen, and so on.

As the number of known elements increased, so did the complexity of understanding their relationships. The introduction of the concept of valence added another layer of complexity to the classification of elements. This growing understanding laid the groundwork for a more comprehensive system of organization, ultimately leading to the creation of the periodic table.

The early efforts to organize elements culminated in the recognition that a systematic approach was essential for advancing the study of chemistry. The groundwork laid by these early chemists paved the way for later developments, making it clear that the understanding of elements would require not just observation but also a coherent framework for classification.

Adding New Elements

Throughout the 19th century, the periodic discovery of new elements necessitated an expanded understanding of classification in chemistry. The discovery of oxygen by Joseph Priestley in the late 18th century, followed by the identification of other gases and elements, highlighted the importance of systematically organizing these substances. As chemists isolated and identified new elements, they found that many exhibited unique properties that could not be easily categorized.

The advent of analytical techniques, such as spectroscopy and electrolysis, allowed scientists to explore the characteristics of elements in greater detail. New discoveries, such as chlorine by Carl Wilhelm Scheele and iodine by Bernard Courtois, further expanded the growing list of known substances. Each new element prompted scientists to reconsider existing classifications and relationships among elements, driving home the need for a cohesive system to organize them.

Scheele theorized about the existence of several elements, such as barium, manganese, and tungsten, but since he wasn’t able to isolate the elements, other chemists got the credit for their discoveries instead. English chemist Humphry Davy isolated barium in 1808; Swedish chemist Johan Gottliebe Gahn isolated manganese in the same year; and Spanish chemists and brothers Fausto and Juan José Elhuyar got to tungsten in 1783.

As new elements were discovered, chemists began to refine their definitions and criteria for classifying substances. The quest to classify and understand these new substances reached a critical point as researchers began to recognize patterns in their properties. The growing realization that elements could be organized based on similarities in their chemical behavior led to the development of more systematic approaches. This period of exploration and discovery set the stage for the significant breakthrough that would come with Dmitri Mendeleev’s periodic table.

Mendeleev’s Table

In 1869, the Russian chemist Dmitri Mendeleev published his periodic table, a groundbreaking organizational tool that arranged elements according to their atomic mass and chemical properties. Mendeleev’s table was revolutionary for its time, revealing periodic trends that allowed him to predict the existence and properties of undiscovered elements. His ability to foresee gaps in the table, such as the prediction of germanium, gallium, and scandium, showcased the predictive power of his approach.

Mendeleev’s periodic table organized elements based on their atomic mass, but he also considered their chemical properties. This dual focus allowed Mendeleev to create a structure that highlighted not only the relationships between known elements but also the potential for new discoveries. For instance, he noted that certain elements exhibited similar characteristics, such as reactivity and valence, leading to the classification of groups or families within the table.

One of the most striking aspects of Mendeleev’s work was his willingness to leave gaps for undiscovered elements. This bold decision demonstrated his confidence in the periodicity of elements and encouraged further exploration and experimentation. Mendeleev’s foresight in predicting the existence of elements such as gallium, which was discovered shortly after the publication of his table, solidified his reputation as a visionary in the field of chemistry.

Mendeleev’s periodic table marked a turning point in chemistry, establishing a foundation for future research and discovery. His emphasis on the periodicity of elements—the idea that properties of elements repeat at regular intervals—helped unify various branches of chemistry and encouraged further exploration into the relationships between elements. This innovative framework allowed chemists to better understand and predict chemical reactions, paving the way for advancements in the field.

Marie Curie and Radioactivity

The early 20th century marked a pivotal era in the understanding of elements, particularly through the groundbreaking research of Marie Curie. Born Maria Skłodowska in Warsaw, Poland, in 1867, Curie moved to Paris to study at the Sorbonne, where she became the first woman to earn a degree in physics and later in mathematics. Her passion for scientific inquiry led her to investigate the emerging field of radioactivity, a term that she coined, which described the phenomenon of certain elements emitting radiation spontaneously.

Curie’s research began in earnest in the late 1890s when she and her husband, Pierre Curie, embarked on a study of uranium rays. They discovered that uranium was not the only element capable of emitting radiation. This realization prompted them to explore other minerals that contained uranium, leading to the identification of two previously unknown elements: polonium and radium. The Curies meticulously isolated these elements from uranium ore, a labor-intensive process that required grinding up ore samples and dissolving them in acids for several hours.

The implications of Curie’s work were profound, as her research demonstrated that some elements could decay and emit energy in the form of radiation. This challenged the prevailing notion of atomic stability and led to a deeper understanding of atomic structure. Her work also had significant health implications, as it became clear that exposure to radioactive materials could have harmful effects, leading to both medical advancements and concerns about safety.

Marie Curie’s dedication to her research was remarkable, often putting her own health at risk. She worked in poorly equipped laboratories and frequently handled radioactive materials without the protective measures that are standard today. Her commitment to advancing scientific knowledge eventually took a toll on her health, but she remained undeterred in her pursuit of discovery. In recognition of her groundbreaking contributions, Curie became the first woman to receive a Nobel Prize in Physics in 1903, shared with Pierre Curie and Henri Becquerel.

In 1911, Curie was awarded a second Nobel Prize, this time in Chemistry, for her discoveries of radium and polonium. This achievement solidified her legacy as a pioneer in the field and highlighted the significant role women could play in science, a rarity in her time. Her contributions not only advanced the understanding of radioactivity but also opened new avenues in medicine, particularly in cancer treatment, where radium was used for radiation therapy.

Curie’s work laid the foundation for future research in nuclear physics and medicine, influencing countless scientists and practitioners. The establishment of the Curie Institutes in Paris and Warsaw further exemplified her commitment to science, as they became centers for research in cancer treatment and radioactivity. Marie Curie’s life and work exemplify the profound impact of scientific inquiry, illustrating how one individual’s dedication can transform our understanding of the natural world.

Synthetic Elements

The mid-20th century ushered in the era of synthetic elements, significantly expanding the periodic table and challenging traditional notions of elemental stability. The first synthetic element, technetium (Tc), was created artificially in 1937 by Italian scientists Carlo Perrier and Emilio Segrè. This element was created artificially in a laboratory through the bombardment of molybdenum with deuterons in a cyclotron. Technetium’s discovery was groundbreaking because it was the first element that did not have any stable isotopes and was not found naturally in the Earth’s crust, highlighting the possibilities of nuclear chemistry and the ability to create new elements.

As advancements in nuclear physics progressed, the understanding of atomic structure and nuclear reactions evolved, leading to the synthesis of heavier elements. The development of particle accelerators allowed scientists to conduct experiments that could create new elements by colliding lighter nuclei at high energies. This opened up a new realm of possibilities in chemistry, leading to the discovery of several transuranium elements— elements with atomic numbers greater than uranium (92). Notable examples include neptunium (Np) and plutonium (Pu), discovered in the 1940s by Edwin McMillan and Glenn T. Seaborg, respectively.

The synthesis of these new elements had profound implications for both scientific research and practical applications. Plutonium, for instance, played a critical role in the development of nuclear weapons during World War II. Its discovery and subsequent use in the Manhattan Project exemplified the dual-edged nature of scientific progress, where groundbreaking discoveries can lead to both beneficial and destructive outcomes. This highlighted the importance of ethical considerations in scientific research, particularly in the context of nuclear chemistry.

Nuclear containment strategies aren’t always foolproof. In 1986, the Chernobyl disaster in Ukraine resulted from a flawed reactor design and operator errors, leading to a massive release of radioactive materials and long-term environmental contamination. The incident exposed severe shortcomings in safety protocols and containment measures, resulting in widespread health issues and displacement of communities. Similarly, the 2011 Fukushima Daiichi nuclear disaster in Japan, which was triggered by a devastating earthquake and tsunami, demonstrated the vulnerabilities of nuclear facilities to natural disasters. The failure of containment systems led to meltdowns and significant releases of radiation, prompting evacuation and ongoing concerns about the safety of nuclear energy.

Synthetic elements often exhibit radioactive properties, which have both benefits and challenges. The use of radioactive isotopes in medicine, particularly in diagnostics and treatment, has revolutionized healthcare. Isotopes such as iodine-131 and cobalt-60 are used in cancer treatments, showcasing the potential of synthetic elements to improve human health. However, the radioactive nature of these elements also raises concerns about safety and environmental impact, emphasizing the need for careful handling and regulation.

The ability to create and study synthetic elements enriched the periodic table and opened new avenues for exploration in chemistry. Researchers have synthesized elements up to number 118. Each new addition expands our understanding of atomic behavior and the underlying principles of chemistry, pushing the boundaries of what is known and challenging scientists to rethink fundamental concepts.

Vocabulary List

Root Language of origin Meaning Example
irid/iris Greek rainbow, colorful, iris iridescent
mer Greek part polymer
mes Greek middle Mesoamerica
krypt/crypt Greek hidden krypton
bar(i/y) Greek heavy barometer
iod(e) Greek violet iodine
brom Greek stench, stink bromide
cycl(o/e) Greek circle bicycle
mall(e) Latin hammer mallet
tellu(r/s) Latin earth tellurian
nucle(us) Latin nut, nutshell nucleus
radi(o) Latin ray (as of the sun) radiant
med/mid(i) Latin middle median
fug(a) Latin to flee, to go away from fugue
pet(it) Latin to seek, to go towards petition
gress/grade Latin to go, to advance progress

Vocabulary Practice

Practice Set A: Identify the roots in each of the following words, give their language of origin, and their definitions. Also give their part of speech. Then, following the guidelines in Lesson 4, arrange the definitions of the individual roots to create a literal definition.

  1. synthetic
  2. radioactive
  3. isotope
  4. thermonuclear
  5. periodic
  6. malleable
  7. ductility
  8. centripetal
  9. centrifugal
  10. cryptography
  11. regression
  12. primary
  13. barium
  14. iodine
  15. bromine
  16. iridium
  17. krypton
  18. technetium
  19. spectroscopy
  20. deuteron

Reflection Questions

  1. What similarities do you see between the naming of elements and the naming of biological organisms in rank-order taxonomy? What differences do you see?
  2. Some elements are named after certain places. Look up the origins of the names for gallium and francium. What do they have in common?
  3. How did the development of nuclear science during World War II impact the ethical considerations surrounding its use? What ongoing ethical debates are present in the field today?
  4. Read the International Union of Pure and Applied Chemistry (IUPAC)’s guidelines for the naming of a new element.Do these guidelines seem reasonable to you? Are there any elements that don’t follow these guidelines?