The Periodic Table And Its Elements

By

Miha Alam

History:

·         The first contribution towards elements was made by Aristotle, a famous Greek philosopher. In 330 BC, he gave the “four element theory” which meant that there are four main elements in this world which are earth, air, fire and water.

·          A thought which occurred in peoples mind was how small can particles get when we break down something. Next contribution was made by a famous scientist called Henning brand who was the first person to discover phosphorus. These discoveries lead to a question that how is substance an element?

·         This question was answered by Boyle in 1661, gave a definition that “an element as a substance that cannot be broken down into a simpler substance” which basically means that elements are matter which cannot be broken into simpler form.

·         In 1770-1789, Antoine Lavoisier wrote the first list of elements. He wrote these 33 elements by separating metals and non-metals. Lavoisier wrote a book, with list of elements. It included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur, light and caloric. He also classified the elements as non-metals and metals.

·         In 1772, Daniel Rutherford discovered nitrogen.

·         In 1774, Joseph Priestly discovered oxygen.

·         In the same year 1774 cart Wilhelm discovered chlorine.

·         In 1776 hydrogen was discovered by Henry Cavendish.

·         In 1807, Sir Humphry Davy discovered sodium.

·         In the same year (1807), Sir Humphry Davy discovered potassium.

·         In 1808, Sir Humphry Davy discovered magnesium and calcium.

·         In 1811, Barnard Courtois discovered iodine.

·         In 1818, Johan August discovered lithium.

·         Then after noticing more patterns, Johann Wolfgang Döbereiner in 1827, began to classify the elements in "triads".

o   chlorine, bromine, and iodine

o   calcium, strontium, and barium

o   sulfur, selenium, and tellurium

o   lithium, sodium, and potassium

·         In 1825, Hans Christian discovered aluminum.

·         In 1828, Jöns Jakob Berzelius developed another table with the atomic weights. He also made the letters to symbolize the elements. For example: “Ca for calcium.

·         In 1864, John Newlands, arranged the discovered elements according to the atomic weigh. After observing the similarities between the elements he made the theory of the octaves known as the “Law of octaves”.

·         In 1868, Pierre-Jules-Cesar Janssen discovered helium.

·         In 1869, Lothar Meyer produced a periodic table with 56 new elements which were newly discovered. He arranges them based of the basic characteristics and properties such as atomic mass and molar volume.

·         In the same year (1869), Dmitri Mendeleev also produced a periodic table based on the atomic weight. However, It was arranged in a proper format (like nowadays). All the elements which have same characteristics were displayed together. He left out many gaps so that the undiscovered elements can be placed there. He left gaps by predicting the properties and characteristics of the elements. (for example the atomic mass, atomic number, melting point and the boiling point etc)

·         In 1894, William Ramsay discovered the “noble gases” .

·         In 1914, Henry Moseley                identified the atomic number of the known elements.  He therefore also made some changes in the “periodic law” that atomic numbers affect the properties and the characteristics of an element.

·         In 1940, Glenn Seaborg discovered heavy metals like transuranic elements and placed it after uranium in the periodic table.

It is called the periodic table because there is a pattern which is repeated throughout by the elements. There are many patterns like the elements are listed in increasing order by the atomic number and this is repeated throughout in the periodic table, therefore it is called periodic.

The Periodic table has helped the chemists for example Mendeleev to predict the properties and characteristics of the missing and “not yet discovered” elements. He predicted the properties of the missing elements and completes his periodic table. Later when further research was done, he did some experiments and found out that most of his prediction and hypothesis was accurate which made it easier for him to create the most accurate periodic table. The periodic table also helped in finding the elements. When Mendeleev predicted the properties of the missing elements, he got to know that there are some elements which are yet to be discovered. This was an indication that there are other elements present out their which have to be discovered. The periodic table made it easier for the scientists to find the elements and place them in the right place on the periodic table. On the other hand, the periodic table is still helping us. The periodic table has helped other chemists to make or create elements which lasted for few seconds. One big and major example is the big bang theory. The periodic table helped the scientists arrive at this theory and now they are finding ways to prove it by performing experiments.

As the scientists started to discover more and more elements, they needed to process the data and write it in a way that it is organized, logical and most important makes sense or in other words be meaningful. After identifying patterns and similarities between these elements, they scientists started placing them into a table. In 1863, John Newlands divided the 56 elements which were found into 11 groups based on similar characteristics. The elements are arranges according to the atomic number. Then the elements are arranged according to its characteristics. For example: the elements in the first group are all explosive and highly reactive with water. Then another way the scientists have classified these elements is by putting it under the “11 groups”. John Newlands divided 56 elements into 11 groups according to the similar characteristics like chemical reactions with various substances, atomic mass and numbers. As more and more elements were discovered the periodic table looked like this (see below).

This is the first periodic table made and structured properly by Mendeleev who is also known as the “father of the periodic table”. He left some gaps by predicting some of the characteristics of the missing elements. “www.aip.org/periodic/history.htm”.   

This periodic table is set up in rows and columns. Each row is same because each element share a similarity.  Each row has the same number of the “atomic orbital”. The first row has only one orbit ring for electrons. The second row has two orbit rings for electrons and so on. Just like row, each column has some thing similar too. Another name for a column is “group”. Each element in that group has the same number of electrons in their outer shell but there are always some exceptions. These groups have special names. The main groups are:-

Group 1: Alkali metals
Group 2: alkaline earth metals
Group 3: transition elements
Group 4: metals
Group 5: metalloids
Group 6: non-metals
Group 7: halogens
Group 8: noble gases

Most of the time, each element in each category or column behave similarly to the others. For example the first group is called “alkali metals”. They all are explosive in water, therefore they behave similarly. The only difference in the chemical reaction is that the elements become highly explosive as you go down the table for example:  cesium or rubidium is more reactive and explosive in water than lithium when they go through the chemical reaction.  Alkali metals are metals which are very reactive metals and do aren’t found in nature. All alkali metals have one electron in their outer shell. They all are ductile, malleable, shiny, good conductors of heat and electricity since they are metals. They are usually softer than the other metals and therefore are easy to cut as observed while doing a class experiment. Lithium, sodium, potassium, rubidium, cesium and francium are the alkali metals. Alkaline earth metals are metals just like alkali metals but with slightly different characteristics. Alkaline earth metals are metallic. They are also very reactive since they have the +2 for oxidation. Their presence in nature is very rare since they can be extremely dangerous since they are highly reactive metals. Beryllium, Magnesium, Calcium, Strontium, Barium, Radium belong to the second group in other words the “alkaline earth metals” group. The fourth group is called the metals. They are all ductile, malleable, shiny, good conductors of heat and electricity. Most of them have high melting points. Metals are usually strong, hard and sonorous. The fifth group is “non-metals”. Non-metals are poor conductors of heat and electricity. They aren’t strong or hard-wearing. Most of the non-metals are dull and brittle, which means that the force between the atoms isn’t that strong and their electronic structure is weak. Next is halogen. Halogen means “salt-former”. The reason why halogens are unique is because they all are present in different states of matter in room temperature. For example: iodine and astatine are solids, bromine is liquid and fluorine is gas at the room temperature. The eighth group is called the noble gases. The noble gases are non-reactive metals because their electronic structure is stable. In other words these elements have 8 electrons in their outer electronic shell. This is another reason why they cannot go through chemical reactions and make compounds.