History of the Periodic Table

Introduction to the Periodic Table The periodic table is a widely used reference containing information of many elements. The table is used by scientists, students, and others in order to obtain information such as an element’s atomic number, atomic mass, electron configuration, valence electrons, electronegativity, and where each element is placed. Currently, there are 117 elements the table contains and they are arranged in groups and periods and are divided into two main sections, nonmetals and metals.

Antoine Lavoisier ➣A French chemist who revolutionized chemistry ➣Named the elements carbon, hydrogen, and oxygen ➣Discovered oxygen’s role in combustion and respiration ⤷Established that oxygen is made up of 20 percent air by burning phosphorus and sulfur in the air ➣Discovered that hydrogen and oxygen produces water ⤷Burned hydrogen and oxygen producing water and established water is a compound made up of two elements, not an element itself ➣Discovered Sulfur is an element in 1777 ⤷Many experiments were carried out by Lavoisier, resulting in no ways to break down sulfur into simpler substances any further ➣Compiled a list of the clear difference between a compound and an element ➣Proposed a new fundamental law of nature: the law of conservation of mass - mass is neither destroyed nor created during ordinary chemical reactions or physical changes ➣Developed the four different groups of the periodic table: Gases, nonmetals, metals, and earths

Julius Lothar Meyer ➣A german chemist who is well known for his development on the first periodic table of elements ➣Developed a table of 28 elements according to their valance ➣Meyer developed a graph that displays a periodic pattern as the atomic volume rises to peaks and then falls again ⤷Graph is presented on the next page ➣The graph displayed periodic behavior along with the trends that were found in the properties of the elements ➣Developed a periodic table shortly after Mendeleev, but was less successful compared to Mendeleev

Lothar Meyer’s Graph

John Newlands ➣A English chemist who contributed to the development of the periodic table ➣Newlands arranged all the elements known during his time (56 elements) according to the element’s relative atomic mass ⤷When he did this he noticed that each element is similar to the element eight places ahead ➣The table Newlands’ created had some problems, therefore it wasn’t accepted by many other scientists ⤷The problem that occurs was Newland put iron in the same group as oxygen and sulphur, two non-metals (shown in the table below) ➣Proposed Law of Octaves ⤷States that if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements

Dmitri Mendeleev ➣A Russian chemist who is best known for his discovery of the period law and for his establishment of the periodic table of elements\ ➣Mendeleev arranged the elements by their mass and proposed that certain properties periodically re-occur ➣Although Julius Meyer did something similar shortly after, Mendeleev was more successful ⤷His table exhibited more accurate atomic masses and contained blank spaces for unknown elements at the time (Table shown on next page) ⤷He predicted the properties for five future elements ➣Discovered physical and chemical properties of the elements were related to its’ atomic mass in a periodic way thus arranged the elements with similar properties in vertical columns

Henry Moseley ➣An English physicist who rather than arranging the elements of the periodic table by their atomic weight, he arranged them by their protons and atomic numbers ➣He used a device called an electron gun in order to fire a stream of electrons towards elements and found that the elements give off x-rays ⤷By measuring the frequency of the x-rays from each element, Moseley was able to find the elements’ atomic number or its’ protons ⤷This resulted in a more accurate positioning of the elements (table shown on next page) ➣Moseley predicted the existence of four unknown elements that were yet to be discovered ⤷Now called technetium, promethium, hafnium, and rhenium

Conclusion These five scientist contributed to a huge part of the periodic table. Their contribution lead to the existence of the modern day periodic table, which is widely used by many today. These scientist revolutionized and transformed science all together. The periodic table allows us to have a better understanding of the elements that we may either come in contact with or elements that are rare or not found in nature (lab made elements). The periodic table of elements that we know today is extremely necessary and useful in the chemistry that we study.

Citations http://periodic.lanl.gov/about.shtml http://www.famousscientists.org/antoine-lavoisier/ http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/patterns/perio dictablerev3.shtml http://www.rsc.org/Education/Teachers/Resources/periodictable/pre16/order/atomi cnumber.htm http://www.famousscientists.org/henry-moseley/