• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Third

Extracts from this document...

Introduction

Salters Open Book Paper April/May 2004 One of the earliest attempts to organise chemical elements was that of Johann Dobereiner, who was a German scientist. He noticed that there were several groups of three elements that had similar properties, and that the middle of these (when ordered by atomic weight) had a weight roughly equal to the mean of the other two. Although Dobereiner's contemporaries looked upon these discoveries as mere coincidences, they were important and the idea of trends in the properties of elements was born. Triad 1 Triad 2 Name Atomic Mass Name Atomic Mass First element calcium 40.1 lithium 6.9 Third element barium 137.3 potassium 39.1 Average mass 88.7 Average mass 23.0 Second element strontium 87.6 sodium 23.0 Doberiener's Law of Triads [1]. Note the similarities between the average mass of the first & third elements, and the second. All the elements in a given Triad have similar chemical and/or physical properties. In 1863, the British scientist John Newlands noticed that a pattern occurred in every eighth element when they were organised in order of increasing atomic mass, note that at this point the noble gases were yet to be discovered. ...read more.

Middle

The modern Periodic Table is the result was a combination of many scientists' work. Although it was invented by Mendeleev, it followed from ideas first proposed by Newlands and Dobereiner, and was revised by Mosely, who realised that it worked much better if the elements were arranged by atomic number as opposed to atomic weight. The French scientist Paul Emile Lecoq de Boisbaudran discovered gallium in 1875, by a technique known as atomic emission spectroscopy. This uses an electric arc to excite atoms. The excited atoms then emit light and a prism is used to split this so that the emission spectrum for the sample is shown. The atoms absorb photons of radiation and use this to promote electrons to higher energy levels. The energy level can be described as quantised, that is; fixed quantities of energy are absorbed or emitted when electrons move between different energy levels. As each element has a different electronic structure, each element therefore also has its own unique emission and absorption spectra. When de Boisbaudran found a new, unique, set of emission spectra it was obvious that he had discovered a new element. ...read more.

Conclusion

Increasingly, more and more developments in the world of chemistry are adding to our bank of knowledge concerning atoms, their structure and the ways they behave. It is necessary to have a comprehensive knowledge of these things, in conjunction with a great deal of ingenuity and luck in order to be able to make new and exciting discoveries. Using the (incorrect) theory that atoms are the smallest particles of matter, such techniques, as emission spectroscopy would never have been developed, as this requires complex knowledge of sub-atomic particles and their behaviour when energised. Quantum theory is very important in the development of the Periodic Table as it explains the structure of the atom and the movements and energies of particles on an atomic scale, which is very different to the rules of physics governing the macro world we experience on a day to day basis. Modern chemists have moved from merely discovering elements to creating them. In order to do this; the UNILAC accelerator is required. A beam of heavy ions are fired at a sample of a heavy yet stable element, lead is a common choice. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Classifying Materials section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Classifying Materials essays

  1. Marked by a teacher

    Chemistry revision notes. Atomic Structure and Bonding, Electrolysis, Acids and Alkalis.

    5 star(s)

    Cooling down a reaction will make it slower, this means that food will deteriorate more slowly at low temperatures (e.g. in a fridge or freezer) Remember that raising temperature does not make any difference to the amount produced, only to the speed of the reaction.

  2. Marked by a teacher

    Chemistry Revision Notes on atomic structure, nuclear power and the periodic table

    4 star(s)

    > Nuclear energy is produced in nuclear reactors. The following is a diagram highlighting this process. > Inside a nuclear reactor, uranium fuel is sealed inside rods within the reactor core. When a neutron strikes a uranium atom, the atom undergoes radioactive decay where the uranium atom will split and release three 'free' neutrons and energy.

  1. Free essay

    Periodic table

    Phosphorus - P 16. Sulphur - S 17. Chlorine - Cl 18. Argon - Ar 19. Potassium - K 20. Calcium - Ca The group number is the number of electrons in the outside shell. The period number refers to the number of shells containing electrons. The atomic number is the Protons and the neutrons in an atom.

  2. Classify and identify different polymers to determine their physical properties and uses.

    not be used for high temperature purposes, as they burn easily and almost instantly. It was obvious that the nylon and perspex were both thermosetting polymers, however, both burnt in completely different ways. The perspex, which is reasonably thick, was only charred, however the nylon, a rather scrawny material, disintegrated within 15 seconds.

  1. Rate of reaction of different concentrations of sodium thiosulphate.

    middle of the bottom of the beaker were it can be seen clearly. Step 5- Then pour in the 5cm3 of hydrochloric acid into the solution insure no splashes are made that will decrease the volume of the solution.

  2. The role of mass customization and postponement in global logistics

    The production process must be very flexible in order to meet those requirements. There is no finished-goods inventory -- there can't be if the product is really customized. The lack of inventory has advantages (low carrying costs)

  1. Particulate Nature of Matter

    then look at the dust particles under a microscope, the dust particles will appear to dance around, quite randomly. This zigzag motion happens regardless of how still the water is. The phenomenon was discovered in 1827 by the British botanist Robert Brown.

  2. Determination of the relative atomic mass of lithium

    a mass of 33.25 cm3 Number of LiOH in 100cm3 of the solution from method 1 Finding the original RAM of Lithium Possible hazard of the experiment- the possible hazards that can be encounter could be the reaction of the lithium with the lithium because it is really important that

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work