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

Development of the periodic table.

Extracts from this document...

Introduction

Development of the periodic table The periodic table developed gradually by contributions from various scientists. This eventually led to the modern periodic table. 1. Dobereiner began with the development by grouping elements based on their similarities and classified them using their relative atomic mass. Dobereiner also identified a 'triad' in the list of elements. Calcium, strontium and barium had similar chemical properties. He noticed that the atomic weight of strontium fell midway between the weights of calcium and barium. (Ca 40.1 + Ba 137.5) � 0.5 = 88.7 Sr = 87.6 2. In order of increasing atomic weights, Newlands pointed out that every eighth element had similar properties, e.g. Hydrogen and Lithium (see fig.1). He called this the 'Law of Octaves'. 3. Mendeleev placed elements according to their increase in atomic mass. He left gaps for undiscovered elements. Mendeleev predicted the properties of the unknown elements based on their 'periodic properties', (see fig. 2). Two of these elements he named 'eka- aluminium' and 'eka- silicium'. 4. Reyleigh and Ramsey reported the discovery of noble gases. ...read more.

Middle

The properties of gallium make it hard to classify it as either a metal or a non metal as it has characteristics of both. Like aluminum, it dissolves in both acids and alkalis, evolving hydrogen. This is because both elements are in the same group; therefore their reactivity with other molecules is similar. Aluminum and gallium with Hydrogen ions: 2Al (s) + 6H+ (aq) 2Al �+ (aq) + 3H2 (g) 2Ga (s) + 6H+ (aq) 2Ga �+ (aq) + 3H2 (g) Aluminum and gallium with hydroxide ions: 2Al (s) + 2OH- (aq) + 6H2O (l) 2 [Al(OH)4] - (aq) + 3H2 (g) 2Ga (s) + 2OH- (aq) + 6H2O (l) 2 [Ga(OH)4]- (aq) + 3H2 (g) (Article 1) Very few metals behave in this way which also shows gallium is unusual. This supports the idea of aluminum and gallium being very similar in properties, clearly proving Mendeleev's predictions to be correct. Techniques to increase knowledge of chemical elements There are two main in ways in which chemists have increased their knowledge on chemical elements. ...read more.

Conclusion

Through this technique, chemists found that Nuclei repel because they have a positive charge and that chemical reactions involve loss or gain of electrons. Scientists can strip off the electron shells from even very heavy atoms. 'This allows them to study quantum electrodynamics the most precise theory in physics to unprecedented levels of accuracy' (GSI in profile). The elements that are unstable and have a very short half-life and have decayed long ago are only known to us through UNILAC accelerator. Fig 6, Particle beam target Discovering to synthesizing elements The discovery of elements began before the time of Newland's table. Mendeleev created a table with spaces for new elements to be discovered. The remaining elements were found in the last 140 years, including the noble gases. Techniques such as atomic spectroscopy supported the discovery and production of new elements. Through time, the development of understanding of the arrangement of electrons in atoms has helped to explain the patterns of behaviour and properties of elements. Scientists began to synthesize elements, (turn an element into another). New ways of producing elements were discovered such as the UNILAC accelerator. "... the exception proves the rule." (article 1) Sources Websites: www.hull.ac.uk/hull/chem-web/lectures/06217b/atomic-spec.html www.cerncourier.com/triari/article/38/9/9/1 http://fccjmail.fccj.org/~ethall/period/period.htm Books: Chemical Ideas (Salters) Farshea Saail 0095 1 ...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)

    This requires energy so the forward reaction is endothermic When water is added to anhydrous copper sulphate, it turns blue and heat is given out so the reverse reaction is exothermic. This reaction is sometimes used as a test for water.

  2. Marked by a teacher

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

    4 star(s)

    Proton Neutron Electron Charge Positively charged No charge Negatively charged Location of particles Nucleus Nucleus Electron clouds Atomic mass 1 atomic mass unit 1 atomic mass unit 1840 times less that of protons and neutrons > In any atom, it is the number of protons which determines the atomic number of the particular atom.

  1. Peer reviewed

    Revision notes on elements, the periodic table and compounds.

    4 star(s)

    2 METALS & NON-METALS Metallic elements: - Eg: Mercury, Aluminium = Below 'zigzag line' - They are solid at room temperature (except for mercury, which is liquid at room temperature) - Pure metals are usually soft & weak --> They can be made harder & stronger by mixing them with

  2. Free essay

    Periodic table

    Group number 1 electrons contain 1 electron in the outer shell. - If an atom is given enough energy e.g. heat, the electrons will be able to move from one shell to another. Electrons move from a place of either higher energy to a place of lower energy and vice versa.

  1. A practical study of the periodic table.

    We wanted to examine the solubility and pH of the oxides and chlorides and check the volatility by burning all the substances. If the bonding is strong, the substance is not volatile; similarly, if the bonding is weak, the substance is volatile.

  2. The Development of the Periodic Table

    One of the most extraordinary things about gallium is its low melting point of only 29.78�C. This means that is liquid near room temperatures or in hot countries. This is particularly good as it can be used in glass thermometers.

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

    and Home Depot, have implemented delayed differentiation strategies to reduce manufacturing, shipping and inventory costs, while improving order fill rates. Market Inhibitors The Oracle/Cap Gemini Ernst & Young study determined that nearly half of responding companies had not implemented postponement strategies to date.

  2. The modern day periodic table

    Due to its low melting point and a high boiling point of 2403�c Gallium has the widest liquid range of any element. Gallium has a liquid range of 2174.09 K in comparison with the metal Aluminium often described as having similar properties which has a range of 1858.53 K.

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