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John Dalton
He created his atomic theory which is now the essence and base of what we know about atoms. His theory consisted of these four main points.1.All matter is made of atoms. Atoms are indivisible and indestructible. 2. All atoms of a given element are identical in mass and properties. 3.Compounds are formed by a combination of two or more different kinds of atoms. 4. A chemical reaction is a rearrangement of atoms. BIBLIOGRAPHY: "Dalton's Atomic Theory." Dalton's Atomic Theory. N.p., n.d. Web. 0 -
Dalton's Model
Dalton's atomic model is probably the less sofisticated and realistic model because in the creation of his atomic theory, electrons and the nucleus were unknown. Therefore, Dalton's model is just a tiny ball that is the atom.
"Everything Science." N.p., n.d. Web. 05 Sept. 2013. -
William Crookes
Crookes made some progress in the atomic theory. Using its techniques, Crookes discovered (1861) the element thallium, which won him election to the Royal Society. rookes invented the radiometer in 1875 and, beginning in 1878, investigated electrical discharges through highly evacuated "Crookes tubes." These studies laid the foundation for J. J. Thomson's research in the late 1890s concerning discharge-tube phenomena. BIBLIOGRAPHY: "Sir William Crookes." Sir William Crookes. N.p., n.d. Web. 05 -
J.J Thomson
J. J. Thomson – used a cathode ray tube to prove that atoms were made up of positive and negative sub-atomic particles (1897). By manipulating the magnetic field
surrounding the CRT, he found he could "bend" the stream of negatively changed particles.The particles are named electrons and are assigned the charge of -1. BIBLIOGRAPHY: "Joseph John Thomson." Homepage of the Chemical Heritage Foundation. N.p., n.d. Web. 05 Sept. 2013. -
J.J. Thomson's Model (Plum Puddin Atomic Model)
William Thomson (also known as Lord Kelvin) envisioned the atom as a sphere with a uniformly distributed positive charge and embedded within it enough electrons to neutralize the positive charge. BIBLIOGRAPHY: "Thomson Atomic Model." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 06 Sept. 2013. -
Niels Bohr
Niels Bohr – discovers that the energy from electrons is quantized; meaning it can only exist at certain discrete levels, not between (1913).
This notion, that the electrons in an atom are
localized into different energy levels leads to
the birth of Quantum Mechanics and the Bohr
Model of the Atom.
BIBLIOGRAPHY: "Niels Bohr: Biography & Atomic Theory." LiveScience.com. N.p., n.d. Web. 05 Sept. 2013. -
Bohr's Model
The Bohr Model is probably familar as the "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy. In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus. BIBLIOGRAPHY: "The Bohr Model." The Bohr Model. N.p., n.d. Web. 05 Sept. 2013. -
Ernest Rutherford
Ernest Rutherford – Initially famous for the discovery of 3 types of radioactive emissions: ‘a’ particle (we now know is a He nucleus) ‘b’ particle (an electron) ‘g’ ray (no charge, high energy). He was responsible for a remarkable series of discoveries in the fields of radioactivity and nuclear physics. He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. BIBLIOGRAPHY: "Ernest Rutherford." Homepage of the Chemical Heritage -
Rutherford's Model
Ernest Rutherford publishes his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.
BIBLIOGRAPHY: "Rutherford - Atomic Theory." Rutherford - Atomic Theory. N.p., n.d. Web. 05 Sept. 2013. -
Quantum Mechanical Model
The quantum mechanical model was constructed by Erwin Schrödinger. Electrons are defined as standing waves. The quantum mechanical model shows that electrons don’t have set orbital but are in random motion confined within the areas of electron probability distribution. Note: The quantum mechanical model works for all elements whereas the Bohr model works only for hydrogen. BIBLIOGRAPHY: "ATOMIC STRUCTURE." ATOMIC STRUCTURE. N.p., n.d. Web. 06 Sept. 2013. -
James Chadwick
Chadwick was an important piece in the atomic structure discoveries. James was most famous for his discovery of the neutron in an atom. He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle,the neutron. BIBLIOGRAPHY: "James Chadwick -Atomic Theory - Home." James Chadwick -Atomic Theory. N.p., n.d. Web. 05 Sept. 2013.
