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Scientific Model
A mental image of some thing or process that helps one understand it
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A model should be consistent with previous observations and should enable one to predict other
behaviours
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Models
Empedocles model
4 elements model; This model says that every other substance is actually made of the four
elements: air, earth, fire, and water
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As well as some things could not be explained
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C
He was the first person to propose the idea of the Atom
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In the end, he concluded that everything in
the world was made of tiny particles which he named atoms from the Greek word atomos
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He stated that compounds are created when atoms combine to form molecules
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Billiard Ball Theory (1808)
Dalton envisioned the atoms as indivisible billiard ball structures with hooks
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His theory could not explain the electrical nature of
matter
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This
meant that the atom could in fact be divided into smaller parts
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J Thomson
He discovered electrons by placing a positive source near a Cathode Ray Tube
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His
experiments proved the mass of an electron
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109x10^31 or almost no mass at all
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Thomson’s model
Thomson’s model, was discovered with gas discharge tubes which led to the discovery of a
heavier positive particle which later was identified as a proton
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Rutherford’s Experiments
Rutherford fired positively charged alpha particles at the gold foil
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He compared the deflection of these particles to the deflection of a bullet on a piece of tissue
paper
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Problem Could not explain why the negative electrons didn’t get sucked into the
positive nucleus
Bohr’s Planetary Model (1913)
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Niels Bohr refined Rutherford’s model by envisioning the electrons traveling in orbits like
planets around a sun
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Quantum Model (1920)
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It is the current Model of Matter
Proposed by Albert Einstein, Heisenberg and Schrodinger
States that the Atom contains a small, dense positively charged Nucleus that contains
both Protons and Neutrons
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Currently, we have no evidence to change the model yet
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An element can be broken down into smaller fundamental particles which also make up all other
elements
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Carbon’s atomic number is g because each carbon atom contains 6 protons
Atomic Mass (A) the atomic mass of an element is the number of neutrons and protons each of
its atoms have