Chemistry Project - Scientist

My chemistry class was given a variety of scientists that come up on the Leaving Certificate course.

 

Ernest Rutherford

The scientist which i was assigned was Ernest Rutherford. We has to present our project in a scrap book and have all the information hand written.

Below are the notes that I used to complete my project and a few pictures.

Ernest Rutherford – Project Notes

Early background information – nationality, childhood, family, schooling (5

•  Born on the August 30, 1871 in New Zealand
•  4^th of 12 children, the second son
•  His father, James, had little education and struggled to support the large family on a flax-miller’s income.
•  Ernest’s mother, Martha, worked as a schoolteacher. She believed that knowledge was power, and placed a strong emphasis on her children’s education.
•  Nicknamed was ‘Ern’
•  Helped milking the cows etc. on the family farm after school
•  On the weekend he went swimming in to local creek with his brothers
•  Since money was tight they always had to invent
•  Motto in life was, “We haven’t the money, so we’ve got to think”
•  Age of ten he was given his first science book – inspired his scientific mind
•  Very intelligent - In 1887 he was awarded a scholarship to attend Nelson Collegiate School, a private secondary school where he would board and play rugby until 1889.
•  1890 Rutherford landed another scholarship—this time to Canterbury College in Christchurch, New Zealand.
•  Professors fuelled his enthusiasm for seeking concrete proof through scientific experimentation
•  Obtained both his Bachelor of Arts and his Master of Arts degrees there, and managed to achieve first-class honors in math and science.
•  Left for Canada when he was given the opportunity to take the chair of physics at McGill University in Montreal.
•  Married his landlady’s daughter, Mary Newton. The couple married in 1900 and later welcomed a daughter, whom they named Eileen.

Major findings (10)

•  The nucleus in an atom
•  1^st scientific experiment/ break through was his investigations into the disintegration of the elements, and the chemistry of radioactive substances
•  Therefore discovering thorium gas
•  By 1911 he had already spent 4 years in the university of Manchester, which is where he held the chair of physics for 12yrs
•  Began work on his famous scattering experiments
• Came across his second ‘eureka moment’
•  He discovered that they majority of the mass of an atom is found in the centre – nucleus had been discovered.
• Third contribution was the world’s first alchemist to transform nitrogen into oxygen.
•  Result of bombarding nitrogen gas with alpha particles so that higher energy protons were ejected.

Theory related to major findings (20)

·         The gold foil experiment

Gold Foil Experiment

·         JJ Thompson’s theory before Rutherford was…. The plum pudding model explained an atom as a positive charge body which contains small negatively charged particles which are called electrons. He also described that the negative charge in atom is balanced with the equal amount of positive charge to maintain the neutrality of atom

·         There were many faults in his theory, which Rutherford later discovered

·         Rutherford discovered the entire structure of the atom while completing the Gold Foil Experiment carried out in 1898, however only published in 1911

·         His research is based on the experiment with alpha particles. Alpha particles are helium atom particles. He did bombardment of positive alpha particles on thin foil of gold approx. 8.6 x 10 -6 centimetres thick and took the observations on the screen of zinc sulphide which was behind the gold foil. He observed the deflection of these bombarded alpha particles on the photographic film

·         This experiment was determined to find out the structure of an atom. By this time it was discovered by J.J. Thomson that electrons are present in an atom and that they are negatively charged. So it was assumed that since an atom is neutral and electrons present are negatively charged, there should be some positive charge inside it that makes it neutral. So Rutherford worked under the discoveries and assumption of J.J. Thomson.

·         The alpha particles were confined to a narrow beam by passing then through a lead sheet through a slit. An extremely thin gold foil was bombarded with the narrow beam of fast moving alpha particles. On bombarding the alpha particles were scattered in different directions with different angles and were detected by florescent rotatable detector which has a microscope and a screen coated with zinc sulphide. The whole experimental setup was placed in an evacuated chamber to prevent scattering by the air molecules. These particles after striking on the screen caused scintillation's

After performing his experiment he made observations:

• Almost all the alpha particles did pass through the foil but
• Some alpha particles were deflected off at different angles as observed at the screen of the detector.
• Very few of the alpha particles (one or two) even bounced backwards after hitting the gold foil.

On the basis of these observations Rutherford made the following conclusions:

• Since most of the alpha particles passed straight through the gold foil without any deflection, most of the space within the atoms is empty.
• Since some of the alpha particles (which are big in size) were deflected by large angles or bounced backwards, they must have approached some positively charged region responsible for the deflection. This positively charged region is now called the nucleus.
• As very few alpha particles undergone the deflection, it was concluded that the volume occupied by the central region ( nucleus ) is very small.
• Since alpha particles which are relatively denser, were deflected by the central volume of charge, it shows that almost the complete mass of the atom must be within the central volume.

·          His theory is considered to be very important in the history of atomic theories as he was the first who discovered and proved the existence of central positive charge i.e. nucleus inside an atom.

Following are the main points of Rutherford’s theory:

• Most of the part of an atom is empty.
• Approximately all the mass of the atom is concentrated at the center of atom which is now called nucleus.
• In the central region of atom, the positively charged particles are present.
• The charge on the nucleus of an atom is positive and is equal to Z.e where Z is charge number, e is charge of proton.
• The negatively charged particles i.e. electrons revolve around the central positive portion in different circular orbits.
• Central region (nucleus) is very small in size if compared to the size of atom.

There were mainly two defects in Rutherford's atomic theory as follows:

1. Being a charged particle, electron must emit energy when it is accelerated, according to classical electromagnetic theory. We know that around the nucleus, the motion of electron is an accelerated motion, hence it must radiate energy. But this does not happen in actual practice. Assume that if it occurs then due to continuous loss of energy orbit of electron must decrease continuously. As a result electron will fall into the nucleus eventually after some time. But this is against the practical situation and hence this shows that atom is unstable.
2. If the electrons emit energy continuously, continuous spectrum should be formed. But in practical line spectrum is observed.

Prizes awarded for work/recognition (5)

·         several honorary degrees and fellowships from organizations such as the Institution of Electrical Engineers

·         In 1914 he was knighted

·         In 1931, he was elevated to the peerage, and granted the title Baron Rutherford of Nelson

·         elected president of the Institute of Physics that same year

·         Nobel Prize in 1908 Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances.''  - delighted that he had  transformed from a physicist to a chemist.

·         became a Member of the Order of Merit (Civil Badge) in the New Year's Honour's List for 1925

·         In choosing his coat of arms Ern, and the Herald of Arms, worked in Rutherford elements (the legless swifts on the shield), New Zealand elements (the Kiwi and the Maori warrior), past honours (the Order of Merit), knowledge (the left hand supporter is Hermes Trismegistus, the patron saint of knowledge and alchemists) and his own researches (the shield is quartered by the curves of radioactive growth and decay). A translation of the latin motto is To seek the first principles of things, adapted from Lucretius' On the Nature of The Universe.

Other developments based on these findings, by other scientists and Applications to current use (5)

•     Later on the basis of his theory further improvements were made in the structure of an atom by Neil Bohr and other scientists.
•  913, Neils Bohr, a student of Rutherford's, developed a new model of the atom. He proposed that electrons are arranged in concentric circular orbits around the nucleus. This model is patterned on the solar system and is known as the planetary model.
•  In 1926 Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.
•  Until 1932, the atom was believed to be composed of a positively charged nucleus surrounded by negatively charged electrons. In 1932, James Chadwick bombarded beryllium atoms with alpha particles. An unknown radiation was produced. Discovered the neutron

Key points for leaving Certificate exam about your Scientist (10)

•  Radioactivity gave him a new method for probing inside atoms
•  His co – workers for the Gold Foil Experiment were Geiger and Marsden
•  Hydrogen nuclei are produced in the break-up of the nuclei of the bombarded atoms
•  1920 he concluded that the hydrogen nuclei were called protons
•  The proton and the electron carry the same charge
• Suggested that the nucleus contains other particles of equal mass to protons but, with no charge, because hydrogen has one proton and helium had two, but heliums mass was four times the mass of hydrogen

·          

Final Years

•  Died in Cambridge on October 19, 1937, following a short illness, and was (ashes) buried in Westminster Abbey
•  Age 66 from the complications of a strangulated hernia
•  West of Sir Isaac Newton's tomb