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Hwa Chong InstitutionSecondary 2 Lower Secondary Science

Science Term 2 ACE AssignmentOnline Lesson Periodic Table (Task 2)

Name: Keven Loo Yuquan (14) Class: 2I1 Date: 21 January2011

Find out more about one of the following scientists and describe theircontributions to our knowledge about the structure of the atom. In yourreport, you need to include:

full name, place of birth, date of birth and death

a brief description of the type of work the scientists did in his / herlifetime

their contribution to our understanding of the structure of the atom

the technology available to the scientist that enabled him/her to makethe discovery

a description of how relevant the scientist's theory is to today'sunderstanding of the structure of an atom.

Choose from John Dalton, Sir William Ramsay, Marie Curie, J.J. Thompson,Henry Moseley, Max Planck, Eugen Goldstein, Lord Rutherford, FrederickSoddy, Sir James Chadwick, Niels Bohr, Louis de Broglie.

The scientist I have chosen to research about is Marie Curie.

The full name of the scientist is Marie Skodowska Curie. She was born on 7November 1867, in Warsaw, which was then in the Russian Empire, but nowin Poland. She died on 4 July 1934, at the Sancellemoz Sanatorium in Passy,Haute-Savoie, eastern France. The cause of her death was from aplastic

anemia, which was almost certainly contracted from exposure to radiation. Asthe damaging effects of radiation were not clearly known then, much of herwork was carried in a shed without proper safety measures. She had carriedtest tubes containing radioactive isotopes in her pocket and stored them inher desk drawer, remarking on the pretty blue-green light that thesubstances gave off in the dark.

The type of work she did in her lifetime were both related to the field ofChemistry and Physics, and eventually she won the 1903 Nobel Prize forPhysics and the 1911 Nobel Prize for Chemistry. Some of her achievements inher lifetime include: creating a theory of radioactivity (she coined the term),finding methods for isolating radioactive isotopes, and the discovery of twonews elements, polonium (which was name after her birth country) andradium.

Her contribution to our current understanding of the structure of the atominclude:

finding that the activity of the uranium compounds depended only onthe quantity of uranium present. She had shown that the radiation wasnot the outcome of some interaction of molecules, but must come from

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the atom itself. In scientific terms, this was the most important singlepiece of work that she conducted.

formulating the theory of radioactivity, that each atom also containedan amazingly large amount of energy. This was the source of themysterious energy of radioactivityit was a fundamental property ofmatter itself.

discovering radioactivity in thorium, discovering radium and poloniumfrom her experiments with pitchblende and torbernite

demonstrated that radioactivity is not a result of interaction betweenelements but instead is a property of an atom

building the foundation (by her work) for other scientists, such as LordRutherford, to understand the atom further, by providing him with asource of radioactivity in which they could probe the structure of theatom further.

At her time, the technology/items/theories/knowledge that enabled her tomake her discovery was:

The electrometer, a device that she and her brother invented, whichmeasured electrical charge. Using this device, she discovered thaturanium causes the air around it to conduct electricity. This helped herto find that the activity of the uranium compounds depended only onthe quantity of uranium present. She had also shown that the radiationwas not the outcome of some interaction of molecules, but must comefrom the atom itself.

Pitchblende and torbernite. Her electrometer showed that pitchblendewas four times as active as uranium itself, and torbernite twice asactive. She concluded that, if her earlier results relating the quantity ofuranium to its activity were correct, then these two minerals mustcontain small quantities of some other substance that was far moreactive than uranium itself.

Pestle and mortar. She used this in her first attempt to find theunknown element which made pitchblende and torbernite even moreradioactive than uranium.

Differential crystallization, which allowed her work of extracting andisolating pure radium metal to study.

Her theory (theory of radioactivity) has propelled many later scientists toprobe the structure of the atom, and the reason why certain elements areradioactive and why certain elements are not. Also, by discovering twoelements, radium and polonium, she provided scientists with radioactive

materials to work with.(Theory and basics of radioactivity, information taken from:http://weather.nmsu.edu/Teaching_Material/soil698/Student_Material/biologicaloxidizer/Theory.html)

An atom consists of a positively charged nucleus around which there areorbits containing the negatively charged electrons. The nucleus is composedof protons (positive particles) and neutrons (without charge). Atoms of an

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element with a different number of neutrons but the same number of protonswill have the same atomic number but a different mass number (weight), andare known as isotopes. Of course, isotopes can be stable or radioactive. Theterm isotope is used in this report to refer to the radioactive type. Theisotopes are distinguished through the mass number written as superscriptwith the symbol of the element; e.g., 12C and 14C, and 32P and 31P. Although

isotopes can be naturally found in very small quantities, the majorcontribution is related to radioisotopes artificially created in atomic reactors.

The electrons are arranged in a series of orbits, and they balance the positivecharge of the nucleus. If each electron moves in its respective orbit, noenergy is released; however, if any force changes the order of an electron, aquantum of energy is released. That electron may jump to inner orbits, losingenergy each time, until reaching a stable status. Thus, radioactive atoms maydecay into different more stable atoms. One or more types of energy arereleased in this way, depending on the kind of particle given off. Alpha, beta,or gamma radiation may be released; each has specific characteristics andcarries a different amount of energy from decaying atoms. Alpha rays have

the lower penetrating power; beta rays have an intermediate penetratingcapability; gamma rays are similar to the light and x-rays but have the higherpenetrating power, and, therefore, they are the most dangerous of the threetypes of radiation for living tissues. As the isotopes decay to more stableatoms, the amount present also decreases. Thus, the time required for anisotope to lose half of its radioactivity is known as the half-life.