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Atomic Theory Unit Questions and Answers 100% Solved
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Exam of 3 pages for the course Atom at Atom (Atomic Theory Unit)
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Atomic Theory UnitWhy were Democritus's idea rejected by other philosophers of the time? - answer
Democritus could not answer or explain what held atoms together as he did not know.
One said philosopher is Aristotle. He believed that instead of being matter being made
of tiny particles (atoms) that they were all fundamentally air, fire, water, and earth.
Which statements in Dalton's original atomic theory are now considered to be incorrect?
Describe how modern atomic theory differs from these statements? - answer The
indivisibility of an atom was proved wrong: an atom can be further subdivided into
protons, neutrons, and electrons. However, an atom is the smallest particle that takes
part in chemical reactions.
According to Dalton, the atoms of the same element are similar in all respects.
However, atoms of some elements vary in their masses and densities. These atoms of
different masses are called isotopes. For example, chlorine has two isotopes with mass
numbers 35 and 37.
Dalton also claimed that atoms of different elements are different in all respects. This
has been proven wrong in certain cases: argon and calcium atoms each have an atomic
mass of 40 amu. These atoms are known as isobars.
According to Dalton, atoms of different elements combine in simple whole number ratios
to form compounds. This is not observed in complex organic compounds like sugar
(C12H22O11).
The theory fails to explain the existence of allotropes; it does not account for differences
in properties of charcoal, graphite, diamond.
Democritus and Dalton both proposed the concept of atoms. Describe the method each
of them used to reach the conclusion that atoms existed. - answerDemocritus
developed his ideas about atoms
through intellectual thought, whereas Dalton
developed his ideas by performing experiments
and making careful measurements. Because
Democritus used only thought and not controlled
experiments, he had no observable facts to
support his ideas and no means of testing his
theories
Compare and contrast the atomic theories proposed by Democritus and John Dalton. -
answer
What particles are found in the nucleus of the atom? What is the charge of the nucleus?
Be able to draw and label an atom. - answerProtons and neutrons, a positive charge
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