Download C.6A: Atomic Theory

C.6A: Atomic Theory
Picture Vocabulary
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John Dalton
A chemist in the early 1800s who proposed
the first theory to relate chemical changes to
events at the atomic level
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J.J. Thomson
A scientist in the late 1800s who discovered
electrons through his explorations on the
properties of cathode rays
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Ernest Rutherford
A scientist who first described the atom as
having a central positive nucleus surrounded
by negative orbiting electrons
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Niels Bohr
A scientist who developed the modern model
of an atom which expanded on Rutherford’s
description by explaining that electrons travel
only in certain successively larger orbits
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Atomic Theory
The theory of the nature of matter which
states that all matter is composed of tiny
indivisible particles known as atoms
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Postulate
Statements that are assumed to be true
without proof
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Dalton’s Postulates
Fire is a chemical change that can
rearrange, but not destroy atoms.
Four postulates that were used to explain earlier observations
of the behavior of matter:
A) All matter is composed of small, indivisible particles called atoms
B) All atoms of a given element are identical in mass and properties
C) Compounds are formed by a combination of two or more atoms in definite
arrangements in the ratio of small whole numbers
D) Atoms are not created, destroyed or converted into other kinds of atoms
during chemical reactions, they are simply rearranged into new compounds
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Particle (Physics)
A particle made up of two protons and two
neutrons that is emitted from a radioactive
source
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Electron Orbital
The specific regions around the nucleus of
an atom in which electrons travel
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Nuclear Atom
A conceptual model of the atom developed
by Ernest Rutherford in which a small
positively charged nucleus is surrounded by
orbiting negatively charged electrons
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Nucleus
The tiny, very dense, positively charged
region in the center of an atom; made up of
protons and neutrons
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Electrical Charge
A form of charge, designated negative, positive,
or neutral (without charge) that is found on the
subatomic particles that make up all atoms
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