Democritus- stated the idea of atoms. He believed that atoms made up matter, and that they could not be divided no further. These atoms were all composed of the same primary matter with the only differences between them being their size, shape and weight. The differences in these characteristics explained the differences in the properties of the matter around us. John Dalton- In came up with the atomic theory in 1803.1.All matter was composed of small indivisible particles called atoms2.Atoms of the same element are alike in weight and other properties, atoms of different emelements are different in weight and other properties.3. Compounds are formed by atoms that seperate. 4. A chemical reaction is a rearrangement of atoms. Dalton's theory also helped further the concept of atomic weights.
J.J. Thompson- He is givin credit for the discovery of the electron. He founded the electron while doing the cathode ray experiment. He found that cathode rays could be deflected by an electric field Showed that cathode "rays" were actually particles. He believed that matter is electrically neutral and electrons are much lighter than atoms.
Ernest Rutherford- He was known as the father of physics. He discovered the concept of radio active half life. He won the Nobel Prize in 1908. His main discovery happened during his famous gold foil experiment. He is given credit to be the first to split an atom. He is given credit for the proton. He belivied that all the mass was in the center of the atom.
Neils Bohr-1913---Bohr made numerous contributions to our understanding of atomic structure and quantum mechanics. He stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states.
Marie Curie- She studied Uranium and Thorium and called there spontaneous decay Radioactivity. She and her husband were awarded the Nobel prize in 1903. She eventually won it on her own in 1911. She became the first person to receive the award twice. She is credited of radioactivity of an element.
Wener Heisenberg- a German Scientist that is known as a contrubuter to quantom mechanics. He is best known for the uncertainty principle of the quantum theory. The uncertainty principle states by precise inequalities that certain pairs of physical properties, such as position and momentom cannot be simultaneously known to arbitrarily high precision. He was awarded the nobel prize in 1932.
Enrico Fermi- He is known for his work on the first nuclear reactor. He was given the Nobel prize in 1932 for his work on induced radioactivity. He is known as the father of the atom bomb.
Monday, October 25, 2010
Essay Question #1 Jonathan Slonaker Chemistry 1st Period
John Dalton- The English teacher, chemist, and physicist John Dalton, b. Sept. 6, 1766, d. July 27, 1844, is best known for developing the concept of atoms into a scientific theory that has become a foundation of modern chemistry. Dalton's atomic theory provided a model from which definite predictions of atoms could be made. each atom has a characteristic mass and that atoms of elements are unchanged in chemical processes.
J.J. Thomson- Sir Joseph John Thomson, b. Dec. 18, 1856, d. Aug. 30, 1940, is universally recognized as the British scientist who discovered and identified the electron. Thomson demonstrated that cathode rays were actually units of electrical current made up of negatively charged particles of subatomic size. He came up with a theory that negative particles were embeded into a positive mass. He won the Nobel Prize for physics; in 1908 he was knighted.
Ernest Rutherford-Sir Ernest Rutherford, b. near Nelson, New Zealand, Aug. 30, 1871, d. Oct. 19, 1937 formed modern-day views concerning the nature of matter. Rutherford made his greatest discovery; the structure of the atom. A very small, tightly packed, charged nucleus sprinkled with opposite charges in the mostly empty surrounding void.
Werner Heisenberg-German theoretical physicist Werner Karl Heisenberg, b. Dec. 5, 1901, d. Feb. 1, 1976, was one of the leading scientists of the 20th century. He did important work in nuclear and particle physics, but his most significant contribution was to the development of quantum mechanics. He is best known for his uncertainty principle, which restricts the accuracy with which some properties of atoms and particles--such as position and linear momentum--can be determined simultaneously.
Erwin Schrodinger-The Austrian theoretical physicist Erwin Schrodinger, b. Aug. 12, 1887, d. Jan. 4, 1961, was founder of the wave equation. His studies of the application and statistical interpretation of wave mechanics, the mathematical character of the new statistics, and the relationship of these statistics to statistical thermodynamics earned him fame in the scientific community. He also worked on problems of general relativity and cosmology and on a unified field theory. Late in his life Schrodinger studied the foundations of physics and their implications for philosophy.
Wolfgang Pauli-The Austrian theoretical physicist Wolfgang Ernst Pauli, b. Apr. 25, 1900, d. Dec. 15, 1958, was one of the founders of modern physics. He is most famous for his "Pauli exclusion principle," which states that no two electrons in an atom can have the same four quantum numbers.
James Chadwick-The English physicist James Chadwick, b. Oct. 20, 1891, d. July 24, 1974, is known for his discovery of the neutron. His experiments on the bombardment of certain light elements with alpha particles led to the discovery of the neutron.
Gilbert Lewis-The American chemist Gilbert Newton Lewis, b. West Newton, Mass., Oct. 25, 1875, d. Mar. 23, 1946, contributed to the study of thermodynamics, atomic structure, and bonding, as well as to the theory of acids and bases and the teaching of thermodynamics. Lewis's work in thermodynamics led him to confirm H. Walther Nernst's third law of thermodynamics. His atomic model, known as the Lewis-Langmuir octet, and his distinction between ionic and covalent bonds marked great progress in understanding chemical bonding. His acid-base concept, which asserted that a base donates an electron pair and an acid accepts the pair in covalent bonding, superseded the Bronsted-Lowry theory.
Linus Pauling-The American physical chemist Linus Carl Pauling, b. Portland, Oregon, Feb. 28, 1901, has made extensive contributions to structural chemistry and molecular biology.In the early 1950s he proposed the alpha helix as the basic structure of proteins and narrowly missed discovering the double-helix structure of DNA.
John Dalton- The English teacher, chemist, and physicist John Dalton, b. Sept. 6, 1766, d. July 27, 1844, is best known for developing the concept of atoms into a scientific theory that has become a foundation of modern chemistry. Dalton's atomic theory provided a model from which definite predictions of atoms could be made. each atom has a characteristic mass and that atoms of elements are unchanged in chemical processes.
J.J. Thomson- Sir Joseph John Thomson, b. Dec. 18, 1856, d. Aug. 30, 1940, is universally recognized as the British scientist who discovered and identified the electron. Thomson demonstrated that cathode rays were actually units of electrical current made up of negatively charged particles of subatomic size. He came up with a theory that negative particles were embeded into a positive mass. He won the Nobel Prize for physics; in 1908 he was knighted.
Ernest Rutherford-Sir Ernest Rutherford, b. near Nelson, New Zealand, Aug. 30, 1871, d. Oct. 19, 1937 formed modern-day views concerning the nature of matter. Rutherford made his greatest discovery; the structure of the atom. A very small, tightly packed, charged nucleus sprinkled with opposite charges in the mostly empty surrounding void.
Werner Heisenberg-German theoretical physicist Werner Karl Heisenberg, b. Dec. 5, 1901, d. Feb. 1, 1976, was one of the leading scientists of the 20th century. He did important work in nuclear and particle physics, but his most significant contribution was to the development of quantum mechanics. He is best known for his uncertainty principle, which restricts the accuracy with which some properties of atoms and particles--such as position and linear momentum--can be determined simultaneously.
Erwin Schrodinger-The Austrian theoretical physicist Erwin Schrodinger, b. Aug. 12, 1887, d. Jan. 4, 1961, was founder of the wave equation. His studies of the application and statistical interpretation of wave mechanics, the mathematical character of the new statistics, and the relationship of these statistics to statistical thermodynamics earned him fame in the scientific community. He also worked on problems of general relativity and cosmology and on a unified field theory. Late in his life Schrodinger studied the foundations of physics and their implications for philosophy.
Wolfgang Pauli-The Austrian theoretical physicist Wolfgang Ernst Pauli, b. Apr. 25, 1900, d. Dec. 15, 1958, was one of the founders of modern physics. He is most famous for his "Pauli exclusion principle," which states that no two electrons in an atom can have the same four quantum numbers.
James Chadwick-The English physicist James Chadwick, b. Oct. 20, 1891, d. July 24, 1974, is known for his discovery of the neutron. His experiments on the bombardment of certain light elements with alpha particles led to the discovery of the neutron.
Gilbert Lewis-The American chemist Gilbert Newton Lewis, b. West Newton, Mass., Oct. 25, 1875, d. Mar. 23, 1946, contributed to the study of thermodynamics, atomic structure, and bonding, as well as to the theory of acids and bases and the teaching of thermodynamics. Lewis's work in thermodynamics led him to confirm H. Walther Nernst's third law of thermodynamics. His atomic model, known as the Lewis-Langmuir octet, and his distinction between ionic and covalent bonds marked great progress in understanding chemical bonding. His acid-base concept, which asserted that a base donates an electron pair and an acid accepts the pair in covalent bonding, superseded the Bronsted-Lowry theory.
Linus Pauling-The American physical chemist Linus Carl Pauling, b. Portland, Oregon, Feb. 28, 1901, has made extensive contributions to structural chemistry and molecular biology.In the early 1950s he proposed the alpha helix as the basic structure of proteins and narrowly missed discovering the double-helix structure of DNA.
Dalton Levy
Democritus - Formulated an atomic theories for cosmos. during the 19th century and helped understand the atomic structure.
Lavoisier- He stated the first version of the law of conservation of mass and he also recognized and named oxygen and many more. He also helped construct the metric system.
John Dalton- He is best known for his pioneering work in the development of modern atomic theory, and his research into color blindness. his beliefs are sometimes referred to as Daltonism, in his honor.
J.J. Thomson- He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer. Thomson was awarded the 1906 Nobel Prize in Physics for the discovery of the electron and for his work on the conduction of electricity in gases.
Ernest Rutherford-In early work he discovered the concept of radioactive half life, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation.
Marie Curie-creation of a theory of radioactivity, techniques for isolating radioactive isotopes, and the discovery of two new elements, polonium and radium. Under her direction, the world's first studies were conducted into the treatment of neoplasms using radioactive isotopes
Enrico Fermi- work on the development of the first nuclear reactor and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics.
Atomic theory history
Examine the history of the development of the atom. We have already discussed the major players in the development of the atom. Pick out at least 8 major players who helped aid in the development of the concept of the atom. Explain each experiment in a concise explanation. Then explain how each one aided in the development of the next or how their concept assisted in the further development of the current quantum model of the atom.
Democritus - (460 B.C.) that everything is composed of "atoms", which are physically, but not geometrically, indivisible. He tested how many times could you physically break something down till it was impossible to break down any more. The Democritean atom is an inert solid that interacts with other atoms mechanically.
Lavoisier- He was intrigued by Democritus’ findings and began looking with more detail at the atom. He is credited with the defining elements. He made the first example of a heliostat, which was used to capture sunlight
John Dalton- He introduced the atomic theory. (All matter is composed of atoms) (Atoms of the same element are alike in weight and other properties, atoms of
different elements are different in weight and other properties.)(Compounds are formed fromed by the union of separation of definite number of atoms.)(Atoms do not divide in chemical reactions; only whole atoms unite with other other
atoms.)
J.J. Thomson- Looked more into Daltons’ theory, and cathode rays. He found that these rays are streams of particles much smaller than atoms, they are tiny pieces of atoms. The rays are made up of electrons.
Ernest Rutherford- He researched radioactivity with his gold foil experiment. He shot alpha particles at a sheet of gold and realized that some alpha particles bounced back and others did not, and he thought there must be some kind of small particle or nucleus .
Marie Curie- She studied Uranium and Thorium and called there spontaneous decay Radioactivity.
Neils Bohr- Came up with a structure for atoms. Devolped a structure of atoms that makes up the periodic table of elements.
Enrico Fermi- He made the first controlled chain reaction by releasing energy into the atoms nucleus.
Examine the history of the development of the atom. We have already discussed the major players in the development of the atom. Pick out at least 8 major players who helped aid in the development of the concept of the atom. Explain each experiment in a concise explanation. Then explain how each one aided in the development of the next or how their concept assisted in the further development of the current quantum model of the atom.
Democritus- Democritus stated that matter was composed of small particles called atoms. "The only differences between them is their size, shape and weight."
John Dalton- he made the 5 laws about atoms listed below. they helped the concept of atomic wieghts.
"1. Matter is made up of indivisible atoms.
2. All atoms of an element are identical.
3. Atoms are neither created nor destroyed.
4. Atoms of different elements have different weights and chemical properties.
5. Atoms of different elements combine in simple whole numbers to form compounds."
Mendeleev- he Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. he also helped arrange the periodic table.
J.J. Thompson-
Found that cathode rays could be deflected by an electric field Showed that cathode "rays" were actually particles
Raising Pudding Model -
Matter is electrically neutral and electrons are much lighter than atoms.
Conclusion: There must be positively charged
particles which also must carry the mass of the
atom. Dalton's model is now incorrect because
atoms are divisible.
Rutherford- Studied absorption of radioactivity.
"* Alpha radiation - positive charge - absorbed by a few hundredths of a cm or metal foil
*
Beta radiation - negative charge - could pass through 100x as much foil before it was absorbed
*
Gamma rays - no charge - could penetrate several cm of lead
Rutherford was also able to estimate the charge of an atom by studying the deflection of alpha particles. He found that the positive charge on the atom was approximately half of the atomic weight."
Bohr- helped to understand atomic structure and quantum mechanics and came up with the Bohr model of the atom.
Mosely- arranged the periodic table based on atomic number. this helped later scientists.
Chadwick- "discovered neutron with radioactivity -
"* Proved that neutrons, neutral particles in the nucleus that made up approximately
half the mass of an atom, did exist."
"Atomic Rules
* The number of protons in the nucleus of an atom is equal to the atomic number (Z).
* In a neutral atom, the number of electrons is equal to the number of protons.
* The mass number (M) of an atom is equal to the sum of the number of
protons and neutrons in the nucleus.
* The number of neutrons is equal to the difference between the mass number (M)
and the atomic number (Z)."
sources - wikipedia (quoted text)
Democritus- Democritus stated that matter was composed of small particles called atoms. "The only differences between them is their size, shape and weight."
John Dalton- he made the 5 laws about atoms listed below. they helped the concept of atomic wieghts.
"1. Matter is made up of indivisible atoms.
2. All atoms of an element are identical.
3. Atoms are neither created nor destroyed.
4. Atoms of different elements have different weights and chemical properties.
5. Atoms of different elements combine in simple whole numbers to form compounds."
Mendeleev- he Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. he also helped arrange the periodic table.
J.J. Thompson-
Found that cathode rays could be deflected by an electric field Showed that cathode "rays" were actually particles
Raising Pudding Model -
Matter is electrically neutral and electrons are much lighter than atoms.
Conclusion: There must be positively charged
particles which also must carry the mass of the
atom. Dalton's model is now incorrect because
atoms are divisible.
Rutherford- Studied absorption of radioactivity.
"* Alpha radiation - positive charge - absorbed by a few hundredths of a cm or metal foil
*
Beta radiation - negative charge - could pass through 100x as much foil before it was absorbed
*
Gamma rays - no charge - could penetrate several cm of lead
Rutherford was also able to estimate the charge of an atom by studying the deflection of alpha particles. He found that the positive charge on the atom was approximately half of the atomic weight."
Bohr- helped to understand atomic structure and quantum mechanics and came up with the Bohr model of the atom.
Mosely- arranged the periodic table based on atomic number. this helped later scientists.
Chadwick- "discovered neutron with radioactivity -
"* Proved that neutrons, neutral particles in the nucleus that made up approximately
half the mass of an atom, did exist."
"Atomic Rules
* The number of protons in the nucleus of an atom is equal to the atomic number (Z).
* In a neutral atom, the number of electrons is equal to the number of protons.
* The mass number (M) of an atom is equal to the sum of the number of
protons and neutrons in the nucleus.
* The number of neutrons is equal to the difference between the mass number (M)
and the atomic number (Z)."
sources - wikipedia (quoted text)
Justin Walton Question 1A
-Democritus- He said that everything is composed of indivisible atoms. He said that there is an infinite number of kinds of atoms, and this is why there are differences in the physical matter in our world.
John Dalton- He is credited with developing the first atomic theory that said all matter is made up of atoms, and that all atoms of the same element are identical. The atoms of different elements are different. He also said that atoms can't be created nor destroyed. His work helped to arrange atoms by atomic weight like they are in the current periodic table.
Mendeleev- He discovered that when elements were arranged in order of increasing mass, there was a pattern in elements that were vertically alligned. He discovered this by using cards with element names and various properties listed on them. He would arrange them according to certain characteristics, and on one of these arrangements he noticed a pattern.
J.J. Thomson- Thomson made a groundbreaking discovery in the development of the atomic model when he discovered electrons. He discovered this through his cathode ray experiment. He found that the rays could be deflected by an electric field, and used the deflection to determine the particle's mass. He discovered a particle 2000 times lighter than hydrogen and determined that it was negatively charged.
Rutherford- Rutherford performed the gold foil experiment. He hypothesized that atoms were composed of both positive and negative charges. He then shot alpha particles at a very thin sheet of gold foil and noticed that while most passed straight through, a small amount were deflected. He determined that they were hitting a large positive mass which later became known as the nucleus. He is credited with discovering the proton.
Niels Bohr- He composed the Bohr model of the atom. This described atoms as having small positively charged nucleus' and electrons that orbit in perfect circles, similar to the Solar System. Bohr made many contributions in the development of the atomic bomb.
Moseley-He devised a periodic table sat up by atomic number rather than atomic mass. He also determined a way for the number to be mathematically figured rather than just represent the place the element is on the table. This allowed scientist to understand physical makeup of atoms and develop a better model for the atom.
Chadwick- He is credited with the discovery of the neutron. he discovered this by colliding berrylium atoms which released massive neutral particles. His discovery made it possible for later scientists to construct new elements in the lab.
"Wikipedia," "answers.com"
John Dalton- He is credited with developing the first atomic theory that said all matter is made up of atoms, and that all atoms of the same element are identical. The atoms of different elements are different. He also said that atoms can't be created nor destroyed. His work helped to arrange atoms by atomic weight like they are in the current periodic table.
Mendeleev- He discovered that when elements were arranged in order of increasing mass, there was a pattern in elements that were vertically alligned. He discovered this by using cards with element names and various properties listed on them. He would arrange them according to certain characteristics, and on one of these arrangements he noticed a pattern.
J.J. Thomson- Thomson made a groundbreaking discovery in the development of the atomic model when he discovered electrons. He discovered this through his cathode ray experiment. He found that the rays could be deflected by an electric field, and used the deflection to determine the particle's mass. He discovered a particle 2000 times lighter than hydrogen and determined that it was negatively charged.
Rutherford- Rutherford performed the gold foil experiment. He hypothesized that atoms were composed of both positive and negative charges. He then shot alpha particles at a very thin sheet of gold foil and noticed that while most passed straight through, a small amount were deflected. He determined that they were hitting a large positive mass which later became known as the nucleus. He is credited with discovering the proton.
Niels Bohr- He composed the Bohr model of the atom. This described atoms as having small positively charged nucleus' and electrons that orbit in perfect circles, similar to the Solar System. Bohr made many contributions in the development of the atomic bomb.
Moseley-He devised a periodic table sat up by atomic number rather than atomic mass. He also determined a way for the number to be mathematically figured rather than just represent the place the element is on the table. This allowed scientist to understand physical makeup of atoms and develop a better model for the atom.
Chadwick- He is credited with the discovery of the neutron. he discovered this by colliding berrylium atoms which released massive neutral particles. His discovery made it possible for later scientists to construct new elements in the lab.
"Wikipedia," "answers.com"
Test Question 1A
-Examine the history of the development of the atom. We have already discussed the major players in the development of the atom. Pick out at least 8 major players who helped aid in the development of the concept of the atom. Explain each experiment in a concise explanation. Then explain how each one aided in the development of the next or how their concept assisted in the further development of the current quantum model of the atom.
1) The first atomic theory was made by Democritus in 460 B.C. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms. These atoms were all composed of the same primary matter with the only differences between them being their size, shape and weight. The differences in these characteristics explained the differences in the properties of the matter around us.
2) Couloumb (1780's), France - formulated the Coulomb's law, which states that that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, one of the main forces involved in atomic reactions.
3) John Dalton helped to explain the laws of chemical reactivity; He performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental. Dalton's theory also helped further the concept of atomic weights. By assuming that nature would be a simple as possible, Dalton assumed that the elements preferred to combine in one to one ratios, and was therefore able to tabulate a set of relative weights.
Dalton's theory can be summarized as follows:
-Matter is composed of small particles called atoms.
-All atoms of an element are identical, but are different from those of any other element.
-During chemical reactions, atoms are neither created nor destroyed, but are simply rearranged.
-Atoms always combine in whole number multiples of each other.
4) In 1897, the English physicist J.J. Thomson discovered the electron and proposed a model for the structure of the atom. Thomson knew that electrons had a negative charge and thought that matter must have a positive charge.
5) Robert Millikan (1908), USA - found out the electric charge of the electron. He determined the unit charge of the electron in 1909 with his oil drop experiment at the University of Chicago. Thus allowing for the calculation of the mass of the electron and the positively charged atoms. e = 1.60 x 10^-19 coulombs
6) Ernest Rutherford-1909-1911---British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom. He used the results of his gold-foil experiment to state that all the mass of an atom were in a small positively-charged ball at the center of the atom.
7) Neils Bohr-1913---Bohr made numerous contributions to our understanding of atomic structure and quantum mechanics. He stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states.
Bohr’s Rules:
-Electrons can orbit only at certain allowed distances from the nucleus.
-Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit.
8) In 1931 Chadwick discovered the neutrally-charged neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name, "nucleon.”
1) The first atomic theory was made by Democritus in 460 B.C. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms. These atoms were all composed of the same primary matter with the only differences between them being their size, shape and weight. The differences in these characteristics explained the differences in the properties of the matter around us.
2) Couloumb (1780's), France - formulated the Coulomb's law, which states that that the force between two electrical charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, one of the main forces involved in atomic reactions.
3) John Dalton helped to explain the laws of chemical reactivity; He performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental. Dalton's theory also helped further the concept of atomic weights. By assuming that nature would be a simple as possible, Dalton assumed that the elements preferred to combine in one to one ratios, and was therefore able to tabulate a set of relative weights.
Dalton's theory can be summarized as follows:
-Matter is composed of small particles called atoms.
-All atoms of an element are identical, but are different from those of any other element.
-During chemical reactions, atoms are neither created nor destroyed, but are simply rearranged.
-Atoms always combine in whole number multiples of each other.
4) In 1897, the English physicist J.J. Thomson discovered the electron and proposed a model for the structure of the atom. Thomson knew that electrons had a negative charge and thought that matter must have a positive charge.
5) Robert Millikan (1908), USA - found out the electric charge of the electron. He determined the unit charge of the electron in 1909 with his oil drop experiment at the University of Chicago. Thus allowing for the calculation of the mass of the electron and the positively charged atoms. e = 1.60 x 10^-19 coulombs
6) Ernest Rutherford-1909-1911---British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom. He used the results of his gold-foil experiment to state that all the mass of an atom were in a small positively-charged ball at the center of the atom.
7) Neils Bohr-1913---Bohr made numerous contributions to our understanding of atomic structure and quantum mechanics. He stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states.
Bohr’s Rules:
-Electrons can orbit only at certain allowed distances from the nucleus.
-Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit.
8) In 1931 Chadwick discovered the neutrally-charged neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name, "nucleon.”
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