The Development Of The Atomic Theory Essay

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The Grecian construct of atomos: the atom

Around 440 BC leucippus of Miletus originated the atom construct. He and his student, Democritus of abdera refined it for future usage. Their atomic thought has five major points. All original Hagiographas of leucippus and Democritus are lost. The lone beginnings we have for there atomistic thoughts are inquotations from other authors. Democritus was known as the & # 8220 ; express joying philosopher & # 8221 ; because he enjoyed life so much. At this clip Grecian doctrine was about 150 old ages old, emerging in the 6th century bc, centered in the metropolis of miletus on the Ionian seashore in Asia child, which is now turkey. The work of leucippus and Democritus was further developed by gourmets ( 341-270 BC ) of Samos. He made thoughts more by and large known. Aristotle besides quotes both of them in reasoning against their thoughts. Most of what we know about leucippus and Democritus was found in a verse form entitled & # 8220 ; de rerum natura & # 8221 ; ( on the nature of things ) written by Lucretius ( 95-55 BC ) . This verse form was lost for over a thousand old ages and was discovered in 1417.

These are the basic points of their theory.

# 1 & # 8211 ; all affair is composed of atoms, which are spots of affair to little to be seen. These can non be split any smaller. & # 8221 ; The atomists hold that dividing Michigans when it reaches indivisible atoms and goes on no more & # 8221 ;

Which means there is a bound to division of affair that we can non travel. Atoms are really hard so they can non be divided. In Greek & # 8220 ; a & # 8221 ; means non and & # 8220 ; tomos & # 8221 ; means cut. So our word comes from atomos, intending uncuttable. He reasoned that if affair could be boundlessly divided, it could besides wholly disintegrate and can non be put back together, nevertheless affair can renew. Even though affair can be destroyed by dividing, new things can be made by fall ining other affair together. This procedure is reversible. The thought of reversibility agencies there must be a bound to splitting. If it could be split everlastingly, there is nil to halt it from destructing itself. Epicures insisted on an upper bound besides, that atoms are ever unseeable, it seems obvious ; all affair that can be seen is still divisible, so they can & # 8217 ; t be atoms.

# 2- there is an empty infinite between atoms. & # 8221 ; Unless there is a nothingness with a separate being of its ain & # 8216 ; what is & # 8217 ; can non be moved-nor once more can it be & # 8216 ; many & # 8217 ; since there is nil to maintain things apart. & # 8221 ;

So there is an empty infinite between atoms, or a vacuity. Given that all affair is composed of atoms, so all alterations must be a consequence of motion of atoms. So the motion within the atoms is allowed by a infinite so atoms can travel from topographic point to topographic point.

# 3- atoms are wholly solid. If there is a infinite outside there can non be a infinite interior, which would do to disintegrate. But we knowthis is incorrect, in 1919 Ernest Rutherford discovered the karyon, showing that there is an empty infinite.

# 4- atoms are homogenous ( no internal construction )

The solidarity of atoms agencies that atoms are the same all over, or has no internal construction. There was guess about sub-atomic construction in the 1800 & # 8217 ; s introduced it on solid scientific footing, non until 1897, J.J. Thomson & # 8217 ; s find of the negatron that it had internal construction.

# 5- atoms are different in?

1- there size.

2- their forms.

& # 8221 ; Democritus and leuccippus say thatthere are indivisible organic structures, infinite figure and form & # 8221 ; Aristotle

& # 8221 ; They have all kinds of forms and visual aspects and sizes & # 8221 ; Democritus

Aristotle and others opposed about all of the thoughts of the atom, so most of the information was lost. There is a form of atomic idea but merely a few bookmans gave it existent idea. It wasn & # 8217 ; t until 1803 that john Dalton ( 1766-1844 ) a school teacher put the atom on a solid scientific base. Dalton & # 8217 ; s gift for analysing informations allowed him to acknowledge the connexion between atomic weight and weight dealingss in chemical gases. He was the first to set the thought of atoms and stoichiometry together.

Dalton & # 8217 ; s atomic Torahs are in the undermentioned points.

# 1- all affair consists of bantam atoms called atoms.

The being of atoms foremost came up 2000 old ages ago. Though they remained pure guess for most of this clip.

# 2- atoms are indestructible and unchangeable. Atoms of an component can non be created, destroyed, broken onto smaller parts or be changed into another component. Dalton based this on the jurisprudence of preservation of mass and experimental grounds.

With the find of subatomic atoms after Dalton. Atoms could be broken into smaller pieces.

It was besides discovered that atoms could be changed into different elements. Most don’t consider this a chemical procedure because the karyon is unaffected.

# 3- elements are characterized by the mass of there atoms.

With the find of isotopes, it was found that elements are characterized by their atomic figure, or the figure of protons.

# 4- when elements react, their atoms combine in simple whole figure ratios.

This suggests a practical scheme for finding the atomic weights of atoms. Atomic weights could so be used to explicate the fixed mass per centums of elements in all compounds.

This explained the jurisprudence of definite proportion and multiple proportions.

Some of Daltons original atomic theories were incorrect but the basic constructs ( like chemical reactions can be explained by the brotherhood and separation of atoms and these characteristic belongingss. ) these thoughts are still the rudimentss of modern physical scientific discipline.

While these beliefs were the pillar of atomic theory. The belief that they were strutureless and indestructible was demolished by J.J. Thomson & # 8217 ; s ( 1856-1940 ) find of the negatron in 1897. It was shortly realized that the mass of an atom is from the positively charged negatron. Thomson used cathode beams and passed them through a glass bulb. He changed the way of the beams with an electric field and concluded they were of negative charge. He knew he could travel them with a magnetic field. Sending each beam in opposite waies, he concluded that the atoms ( or atoms as he called them ) were a hundred times smaller. He found the first sub-atomic atoms.

Through Thomson & # 8217 ; s find of the negatron, Robert milikan ( 1868-1953 ) discovered how to find the charge of an negatron. He sprayed bantam beads onto the infinite above two metal home bases. A bead of oil would fall through now and so through a bantam hole in the home base. The rate of autumn was determined by observation through a telescope. Then the stupa home base was connected to a positively charged battery, and the underside was connected to a negatively charged battery. A beam of X raies was passed between the home bases. The rate of autumn of the oil would alter in sudden leaps. He determined it was because of a addition or loss of negatrons. He created an equation for this autumn.

Electric force = E * vitamin E * N

Then in 1909 a adult male named Ernest rutherford ( 1871-1937 ) used alpha atoms to pelt a piece of thin gold foil. He noticed about all went through the gold but 1/8000 would resile back in a wild way. He quoted & # 8221 ; as if you fired a 15 inch naval shell at piece of tissue and the shell came right back and hit you & # 8221 ; from this he concluded that there was a extremely concentrated, really little positively charged nucleus, while negatrons inhabit the furthest from the atom. His experiment was similar to this.

He besides discovered that the figure of protons makes up the atomic figure. And that the figure of protons and neutrons makes up the atomic mass. Some old ages subsequently Neil & # 8217 ; s Bohr ( 1885-1962 ) came up with his theoretical account of the atom. Bohr & # 8217 ; s pattern described how negatrons performed within an atom.

In his theoretical account he stated that negatrons that raced around the karyon would do standing wavelengths. He imagined the orbit as a pilot moving ridge, uninterrupted.

& # 8220 ; It was like a vibrating twine & # 8221 ;

He besides came up with the undermentioned footings.

Energy level- the specific figure of energy that an negatron can hold.

Chief quantum number- the whole number used to place each energy degree.

Land state- the lowest degree of energy

Excited state- when the electrical causes it to travel to a higher energy degree.

Though the information and finds about atomic theory has changed over the old ages, the atom plays a really of import function in our being.

Bibliography

On cyberspace, Atomic Theory 1996.

hypertext transfer protocol: //www.antoin.fsu.umd.edu Dalton & # 8217 ; s Atomic Theory

hypertext transfer protocol: //dbhs.wvusd.k12.ca.us The Greek Concept Of Atomos John L. Park 1996

Parry/ Dietz/ Tellefsen/ Steiner Chemistry experimental foundations pretension hall 1983

G. Raymer-Cantham, Chemistry addison-wesley publishing houses

On cyberspace, Atomic Theory 1996.

hypertext transfer protocol: //www.antoin.fsu.umd.edu Dalton & # 8217 ; s Atomic Theory

hypertext transfer protocol: //dbhs.wvusd.k12.ca.us The Greek Concept Of Atomos John L. Park 1996

Parry/ Dietz/ Tellefsen/ Steiner Chemistry experimental foundations pretension hall 1983

G. Raymer-Cantham, Chemistry addison-wesley publishing houses

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