Untitled Essay, Research Paper

Yazan Fahmawi

T3 IBS Chemistry

Ms. Redman

Historical Development of

Atomic Structure

The idea behind the "atom" goes back to the Ancient Greek society, where

scientists

believed that all matter was made of smaller, more fundamental particles called elements.

They called these particles atoms, meaning "not divisible." Then came the

chemists and

physicists of the 16th and 17th centuries who discovered various formulae of various salts

and water, hence discovering the idea of a molecule.Then, in 1766 was born a man named John Dalton born in England. He is known as the father

of atomic theory because he is the one who made it quantitative, meaning he discovered

many masses of various elements and, in relation, discovered the different proportions

which molecules are formed in (i.e. for every water molecule, one atom of oxygen and two

molecules of hydrogen are needed). He also discovered the noble, or inert gases, and their

failure to react with other substances. In 1869 a Russian chemist, best known for his

development of the periodic law of the properties of the chemical elements (which states

that elements show a regular pattern ("periodicity") when they are arranged

according to

their atomic masses), published his first attempt to classify the known elements. His name

was Mendeleyev, and he was a renowned teacher. Because no good textbook in chemistry was

available at the time, he wrote the two-volume Principles of Chemistry (1868-1870), which

later became a classic. During the writing of this book, Mendeleyev tried to classify the

elements according to their chemical properties. In 1871 he published an improved version

of the periodic table, in which he left gaps for elements that were not yet known. His

chart and theories gained acceptance by the scientific world when three elements he

"predicted"—gallium, germanium, and scandium—were subsequently

discovered In 1856 another

important figure in atomic theory was born: Sir Joseph John Thomson. In 1906, after

teaching at the University of Cambridge and Trinity University in England, he won the

Nobel Prize in physics for his work on the conduction of electricity through gases. He

discovered what an electron is using cathode rays. An electron is the smallest particle in

an atom, whose mass is negligible compared to the rest of the atom, and whose charge is

negative. Though scientists did not know it at the time, electrons were located in an

electron cloud rotating around the nucleus, or center of the atom.Another prominent figure in nuclear physics is a man called Ernest Rutherford, born in

1871. He also was a professor at the University of Cambridge, the University of Manchester

(both of which are in England), and at McGill College in Montreal, Canada. His importance

comes after the discovery of radioactivity in 1896 by a French scientist named Becquerel.

Rutherford identified the three main components of radioactivity: alpha, beta, and gamma

particles. He also found the alpha particle to be a positively charged helium atom. Also,

Rutherford was the first one to discover the true structure of an atom, it having a

central, heavy nucleus with an electron cloud surrounding it. It was Rutherford that,

through experiments such as passing alpha particles through a thin gold foil and watching

some repel, discovered the second constituent of the atom (also the first component of the

nucleus): the proton. The proton has a relative atomic mass of one and has a positive

charge. Rutherford also went down in history as the first man to artificially cause a

nuclear reaction when, in 1919, he bombarded nitrogen gas with radioactive alpha

particles, which resulted in atoms of an oxygen isotope and protons. A unit of

radioactivity, the rutherford, was named in his honor. A colleague of Rutherford’s at

Cambridge University was a man named James Chadwick discovered the third fundamental

particle that makes up the atom: the neutron. This discovery led immediately to the

discovery of nuclear fission and the atom bomb The neutron has a relative atomic mass of

one, and has no positive or negative charge (i.e. it is neutral). It is found in the

nucleus of atoms, along with the proton.

Chadwick was one of the first British

scientists to stress the development of a possible atom bomb. His name was strongly

associated with the British atomic bomb effort, especially during World War II. During the

last two years of W.W.II (1943-1945) Chadwick moved to New Mexico, where he spent much of

his time researching at the Los Alamos Scientific Laboratory, a site chosen by the US

government for nuclear weapon research. The first atomic bomb was developed here with the

help of James Chadwick. Chadwick earned the Nobel Prize for physics in 1935. In the same

era of the development of the atom lived a man, just across the North Sea from these three

learned individuals, in Denmark. Neils Henrik Bohr, born in 1885, was also a considerable

man when it came to nuclear and atomic physics. He moved to Cambridge University in 1911,

working under J. J. Thomson, but soon moved to Manchester to work under Rutherford’s

supervision. He won the Nobel Prize in physics in 1922 for his theory on atomic structure

(also known as the Quantum Theory), which was published in papers between 1913 and 1915.

He based his work around Rutherford’s conception of the atom. This theory, that suggests

that electrons only emit electromagnetic energy when they jump from one quantum level to

another, contributed tremendously to future developing of theoretical atomic physics. His

work helped lead to the notion that electrons exist in shells and that the electrons in

the outermost shell certify an atom’s chemical properties. He later illustrated that

uranium-235 is the singular isotope of uranium that undergoes nuclear fission. The Bohrs

moved to England, and then to the US, where Bohr went to work for the government at Los

Alamos, New Mexico, along with James Chadwick, until the first bomb’s detonation in 1945.

He disapproved complete secrecy of the nuclear bomb, and believed that its consequences

would revolutionize the modern world. He wanted some sorts of international law to watch

over the use of nuclear devices. In 1945 Bohr returned to the University of Copenhagen in

Denmark, where he began developing peaceful uses for atomic energy, such as power plants

using nuclear resources as opposed to fossil fuels such as coal, oil, and natural gases.

Bohr died in Copenhagen on November 18, 1962. In Austria in 1887 a man by the name of

Erwin Schr?dinger was born. He became a physicist best known for his mathematical studies

of the wave mechanics of orbiting electrons. His most famous and important contribution to

the understanding of atomic structure is a meticulous and precise mathematical description

of the standing waves orbiting electrons follow. His theory was published in 1926, and

along with a German physicist’s theory of matrix mechanics, their theories became the

basis of quantum mechanics. Schr?dinger shared the 1933 Nobel Prize in physics with the

British physicist Paul A. M. Dirac for his contribution to the development of quantum

mechanics. Through the centuries that have passed, minds have been boggled, countless

questions have been answered, and many great minds conceived, however, there is no doubt

that there is still much to discover about the atom, such as sub-atomic, elementary

particles.

A whole new generation of great scientists is still to come, to explore and unlock the

universe’s secrets.