The History of the Periodic Table
History of the Periodic Table During the 1860’s, we knew that about sixty elements existed but the organisation of these elements was yet to occur. A method was needed, so many different scientists significantly contributed, and helped out, so that eventually Dmitri Mendeleev managed to finally construct his table: The Periodic Table. This table is completely based on the properties of matter; the properties of these elements can be described, separated and identified. The arrangement of electrons in atoms has helped to show and explain to us the patterns of behaviour of the elements! There are two types of property of matter: physical properties which describe the material as it is, and chemical properties which show us how an element reacts. The idea to create the periodic table came from the idea that we can easily arrange all the elements in a format which would easily show similarity among groups. A long time ago, scientists studied the elements Potassium, Sodium and Lithium and found that they all react alike with water, oxygen and chlorine to produce similar compounds. It had been shown that lithium has a lower rate of reaction than sodium, whereas potassium has a higher rate of reaction than sodium. When you link this with their atomic masses, sodium is yet again the middle element! This same pattern is repeated with other groups of threes, for example: Bromine,
The Development of the Periodic Table
The Development of the Periodic Table In the early 19th century many chemists began to develop their knowledge of analytical chemistry, the classification of compounds, and it soon came necessary to classify the elements. Johan Döbereiner showed in 1817 that atomic weight of strontium lies approximately between that of calcium and barium and that these element showed a number of similar properties and thus should be grouped. He and other leading chemists later went on to show how this was also true for the halogens and the alkali metals. In 1863 John Newlands showed that when the elements were arranged in order of atomic weight every eighth element showed familiar traits and thus a table idea was brought up. He considered that some elements had not been invented so he left gaps to fit his idea however after about 20 elements the table became inaccurate. In 1869 Dimitri Mendeleyev did extensive research to traits of elements, especially valency, and developed his own table which left gaps for undiscovered elements. He also changed the order of some elements as their properties fitted better that way which lead to doubt in the accuracy of the atomic mass of elements and if element should be sorted by mass. For these undiscovered he predicted what properties they would have. When gallium was discovered by Paul Emile Lecoq de Boisbaudran in 1875 Mendeleyev's idea of periodic
The Development of the Periodic Table.
Chemistry Open Book Exam: The Development of the Periodic Table By Osman Khan Lee 12 Early attempts at the Periodic Table Johann Dobereiner The first scientist to classify the elements into similar properties was the German chemist, Johann Dobereiner. He attempted to arrange them in terms of atomic weights- which we now call relative atomic mass. He identified a number of triads which he classified as having the same properties. His discovery enabled him to identify that the mass of the middle element was approximately the average of the other two. E.G. Element Relative Atomic Mass Lithium 6.9 Sodium 23 Potassium 39.1 The table above shows a triad. The middle element's relative atomic mass can be determined by calculating the average of the two around it: RAM of Sodium = (6.9 + 39.1) / 2 = 23 As well as this there were several other triads identified. However, people believed that this theory was merely coincidence, and was therefore not taken very seriously. Dimitri Mendeleev A few years later Dimitri Mendeleev enhanced Newlands periodic table, which was arranged in order of atomic mass but had several flaws. He corrected the weight values of some of the elements which Newlands had incorrectly calculated but also he realised some elements had not yet been discovered. For this reason he left gaps, which Newlands did not. Mendeleev then predicted the
Is the formula of Copper Oxide the same regardless of how it is prepared?
Is the formula of Copper Oxide the same regardless of how it is prepared? Planning Aim: · To find and compare the formula of Copper Oxide using various different samples. Introduction: · Through my preliminary work I have found the following ways of producing samples of Copper Oxide: . Heating Copper powder/turnings in air. 2. Heating Copper Carbonate in air. 3. Heating Copper Hydroxide in air. 4. Heating Copper Nitrate in air. 5. Heating Copper Sulphate in air · Experiments 1, 2 and 3 are all suitable methods of producing Copper Oxide. · I have decided not to perform either of the last two ways because both give off poisonous gasses during production. · I have chosen to perform the following 3 different experiments: . Reducing a pre-prepared lab sample of Copper Oxide 2. Reducing a sample made by heating Copper Carbonate in air 3. Oxidation of Copper Powder Prediction: · I believe that the formula of Copper Oxide will remain the same (i.e. CuO) regardless of how it is prepared. · This is because the valency of both Copper and Oxygen is 2. · Copper wants to lose both of its outer electrons to gain a complete outer shell. Oxygen needs to gain 2 electrons to achieve a complete outer shell. · Therefore the process of Ionic bonding takes place and Copper gives up its 2 electrons to the Oxygen leaving an ionic formula of: Cu²+ O²-
Periodic table
Chemistry In the beginning a long time ago before cars and mobile phones, students spent all day learning about the matter that made up the earth. They had long lessons, wore funny clothes and only had religious holidays. Alchemists people who made up weird potions to live forever or make gold. At the same time a man named Democritus (A teacher) suggested everything in the world was made up of tiny particles that could not be seen. He called them atoms 2000 years later Democritus idea was correct. Scientists today don't rely on weird potions and secret spaces with cauldrons instead they rely on investigations carried out with careful observations. Today there are 112 known elements Building Blocks Atoms are joined together in groups called molecules Atoms can join together to form elements or large molecules of many different shapes Polymer scientific word to describe large molecules e.g. Rubber, Cotton Questions . What is a molecule? Name the 2 compounds that are made up of molecules? Groups of atoms joined together, Carbon dioxide (CO2) and Water (H20) 2. Are all compounds made up of molecules? explain No some can exist in their natural form on their own 3. Name 4 elements that occur naturally as molecules Carbon Dioxide (CO2) and Water (H20) Methane and ozone 4. What are polymers? Give three examples Large Molecules eg plastics. glass and paint
Electrolysis COursework
Electrolysis Coursework Aim: To investigate whether increasing the voltage through a copper sulphate solution increases the amount of copper extracted. Introduction: Electrolysis is the process in which an electric current flowing through a water solution of a chemical breaks that compound up into its component parts. I will be investigating how changing the voltage through an ionic copper sulphate solution, increases the amount of copper extracted on to the anode. I will do this by varying the voltage to calculate the effects of this factor on the original mass and solution mass after. From this I will calculate the difference, so it is easy to compare and evaluate. Apparatus: - Power Supply Unit (PSU) - Top Pan Balance - Wires - Electrodes - Anode - Electrode holder - 20cm³ CuSO4 solution - Small Beaker - Measuring Cylinder Prediction: I predict that the higher the voltage the higher the amount of copper on the cathode. In the same way, I also predict that the lower the voltage the lower the amount of copper on the cathode. Hypothesis: I base my prediction on my belief that when the voltage is low, the current is weak and therefore less can be separated. In the same way I believe that when the voltage is high, the current is strong so more of the solution can be separated. In electricity opposites attract. Therefore the metals ions, that are positively
Investigation of Energy Changes in a Displacement Reaction.
January 2002 Michael Lavery U5W Chemistry Coursework - Investigation of Energy Changes in a Displacement Reaction. Plan Introduction When a metal is added to a solution of another salt metal the reaction between the two brings about an exothermic reaction. In this investigation I aim to discover, as the mass of zinc increases, when energy given out stops rising i.e. how much zinc can react with 50cm3 of 0.5M Copper Sulphate. The reaction is exothermic because energy given out when bonds are made is greater than the energy taken in to break bonds. Zinc + Copper Sulphate ? Zinc Sulphate + Copper ? ? (metal) (metal salt) Zn (s) + CuSO4 (aq) ? ZnSO4 (aq) + Cu (s) Variables The only variable I will alter throughout the experiment is the mass of zinc used; altering only one variable keeps the test fair. I will keep the following variables constant: Volume of copper sulphate used (50cm3) and the concentration of copper sulphate (0.5M) Method Apparatus * Large glass beaker * Polystyrene cup * Thermometer * Measuring Cylinder * Copper sulphate (0.5M) * Zinc (powder) * Small glass beaker * Mass balance * Spatula Diagram . Using the measuring cylinder measure out 50cm3 of copper sulphate and pour this into the polystyrene cup which is in the glass beaker (as shown in the diagram). To make sure the measuring cylinder gives an accurate measurement
