The Age of Discovery of Elements

The Age of Discovery of Elements "The nineteenth century was the golden age for the discovery of

elements. Scientists began to look for patterns of behaviour between

elements."*1 Johann Döbereiner, a German chemist, was the first to

attempt to categorise the elements. He used their atomic weights,

which we now know as atomic masses.

In 1863, John Newlands, produced something that he called the 'Law of

Octaves'. He used this to produce his own version of the periodic

table, but Newlands came across some problems. "After about 20

elements his table became ragged,"*2 Newlands had left no gaps for

undiscovered elements and even had to put two elements in one space.

It was Dimitri Mendeleev, a Russian chemistry professor, in 1869 that

produced a much improved table. He amended many of the atomic weight

values and left gaps for undiscovered elements.

"Mendeleev was so confident of the basis upon which he had drawn up

his table that he made predictions about elements which had yet to be

discovered."*3 Since Mendeleev's table all the gaps he left have been

filled, three of the five elements whose properties he predicted were

found within fifteen years, and a whole new group has been introduced

- the Noble Gases.

Atomic spectroscopy is one way which has been used to increase our

knowledge about chemical elements. It excites atoms which then emit

light; this light can be split by a prism which will show the

'emission spectrum'. It is used widely to find the composition of a

sample, such as blood, or to estimate the content of a substance.

By placing the sampl...

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...ynthesising 'artificial' elements; this is achieved using the UNILAC

accelerator. This involves firing beams of metal ions into a rotating

metal target with greater force, the nuclei of the atoms fuse together

creating a new element.

In 1940, Ed McMillan created the first artificial element - Neptunium.

Over the 25 years Glenn Seabory, of the University of California at

Berkeleydiscovered an entire family of new elements, 94 to 102.

Specimen References:

*1-*3, *6-*9; Article 1 Gallium: a landmark in the history of

chemistry

*4;

http://www.unodc.org/images/odccp/bulletin/bulletin_1954-01-01_3_page005_img005_large.gif

*5; Absorption Spectrum, page 125, SAC Chemical Ideas, George Burton

et al, Heinemann, 2000.

*11 www.ask.com searched UNILAC accelerator

*12-*15; Article 2: The New Alchemist