Periodic Classification of Elements

For the lesson observed the objectives was to explain the trends of the periodic table based on the elements’ valence electrons and atomic numbers. Additionally, students were responsible for applying their previous knowledge in calculating subatomic particles to review the Bohr Models and discus the relationship among families in the periodic table. Students will use the information from today’s lesson to make future judgments on reactivity and bonding created during chemical reactions in the next unit. Lastly, students were to connect the information on elemental properties to previous experiences with their health, commercial products, and everyday life.

The elements were organized by Dimitri Mendeleév. He organized them by properties (columns), groups (horizontal), and atomic number (the number of protons and electrons). This became known as the Periodic Table. And currently there are 118 elements. He also found gaps in which elements that were yet to be discovered were to go, three of these unknown elements were found and identified in Mendeleév's lifetime. The elements today are used in everything and 75% of the 118 elements are metal.

The identity of each element is defined by the number of protons in its nucleus

-Dmitri Mendeleev- first periodic table, organized 63 known elements according to properties, organized into rows and columns and wrote name, mass, and chemical properties on each

What is the atomic structure you may ask? Well, it’s the law stating the structure of an atom. It is composed of a positively charged nucleus containing a certain amount of protons (positive), neutrons (neutral charge), and electrons (negative). The amount of each subatomic particle (proton, neutron, and electron) all depend on what the element is. Now although this statement may seem fairly simple it was most definitely not. People have been studying the atomic structure for more than 300+ years and are still studying it. So after reading this you may wonder who even made this atomic structure up. After hundreds of years of research there is not any one individual who made the structure up but roughly

Mendeleev knew that there would be elements that would fill the entire table, but they were not yet discovered, so he left their spots blank. He organized the table by their increasing atomic mass. In this lab, our job was to mix unknown solutions with known solutions and record what happened once they were mixed. Once we completed our objectives for the lab, we were to group the solutions with similar characteristics like Mendeleev did when he was organizing his table. Unlike Mendeleev, we did not group ours with atomic mass.

Over the course of the last 5000 years, mankind’s knowledge has been constantly advancing. Chemistry, a branch of science, has experienced a tremendous leap and expansions since ancient Greek civilization. One of the major breakthroughs in the advancement in Chemistry was the creation of the Atomic theory, which laid a foundation for the modern-day Chemistry and future of science. The Atomic theory introduced the idea of atoms, which are defined as the discrete units of matter. There are five key scientists that significantly contributed to the Atomic model over a span of thousands of years. They are: Democritus, John Dalton, J.J. Thompson, Ernest Rutherford, and Niels Bohr.

Medieval alchemists “invented new ways to isolate, purify, and concentrate substances” (Challenging Limits). The alchemists established the value of analysis, which was fundamental to what became chemistry. First, it was Antonie de Lavoisier who used the techniques to move into the modern age of chemistry. He started by isolating elements and identifying the basic building blocks of nature. Even Humphry Davy was interested in learning the basic building blocks of nature. Until, in 1898, a new element was discovered that drew many questions to scientists. Radium had glowed in the dark and when photographed seemed to be giving off its own energy. At the time, no one knew that the radium was a deadly poison, which harmed human tissue. However, the effect on photographic plates that radium gave allowed humans to discover x-ray scans. These x-ray scans allow us to diagnose and treat diseases. With all of these elements taken into consideration, scientist began to ask themselves, “what are the elements made

It made finding the elements easier and it was able to be altered for the better of the science community. His table was able to accurately predict the “missing” elements in his chart. Mendeleev was very successful in his scientific career after he created the periodic table and is most famous for that discovery. Mendeleev’s periodic table had some flaws, but he used his periodic table to: • Propose that some of the elements, whose behavior did not agree with his predictions, must have had their atomic weights measured incorrectly. • Predict the existence of eight new elements.

Stanislao Cannizzaro was born on July 13, 1826. When he was younger, he showed great skills in mathematics. He later became an assistant to Rafaelle Piria. Cannizzaro saw his dedication to his work that Piria influenced him to transform his study to chemistry. Cannizzaro later determined the different atomic weights. Dmitri Ivanovich Mendeleev always had a love for history, math, and physics. He attended the University of St. Petersburg where he formed the ideas of chemical compounds. Mendeleev found out that you could simplify the periodic table by separating them into different groups. He arranged them by the atomic weights and then later realized they had similar chemical properties. He had also given predictions of future elements and their properties.

Additionally, Johann Dobereiner began grouping elements with like properties into triads – groups of 3 elements – between 1817 and 1829. His work began in 1817 after he noticed that the atomic weight of Strontium (Sr) was medially between the atomic weights of calcium and

It was discovered by a man known as Friedrich Stromeyer from Göttingen University. He discovered it while trying to solve the problem which was brought up when apothecaries of Hanover, Germany, made zinc oxide. The zinc oxide was discolored instead of being pure white. Stromeyer traced the discoloration to a component which was not known to the world. He produced a blue-grey metal which he called Cadmium after the mineral. Cadmium comes from the latin word cadmia, meaning calamine. Calamine is zinc oxide which Cadmium originated from.

Atomic Number: 7 Atomic Weight: 14.0067 Melting Point: -346.00°F Boiling Point: -320.44° F Density: 0.0012506 g/cubic cm Elemental State at Room Temperature: Gas Element Classification: Non-metal Introduction Nitrogen was discovered in 1772 by Daniel Rutherford. It is one of the most bountiful elements to exist. Nitrogen gas makes up 79.09% of the earth's atmosphere weighing over 4 trillion tons. It is created from liquefied air by the process known as fractional distillation.

Dimitri Mendeleev is best known for the creation of the periodic table, but he is responsible for so much more than that. He the beginning of his career as a professor of Chemistry at the St. Petersburg Technical Institute and the University of St. Petersburg. It was here that he wrote his first textbook. He was teaching classes and found that it was incredibly difficult to find a quality textbook to use. To counteract this, he simply wrote his own titled The Principles of Chemistry. In the process of writing his book, Mendeleev also discovered the periodic law. This states that elements can be arranged in a grid-like arrangement according to their atomic weight due to a recurring pattern of characteristics within all elements. This discovery

“The elements, if arranged according to their atomic weights exhibit an apparent periodicity of properties.”-Original quote from Dmitri Mendeleev. Dmitri Mendeleev was known for assembling the final periodic table and he predicted the arrangement of the elements. It is said in the Kahn Academy article that Dmitri Mendeleev got the idea for the Periodic Table from playing solitaire. He also envisioned the periodic table in a dream after a three day work binge. He also was known for finding thirty elements, with his own element called mendelevium. He managed to predict the location of so many of the elements by arranging the elements that they knew at the time. Much of his work actually involved his use of cards. Dmitri Mendeleev made