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History of the Atom Questions and Answers 100% Solved
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Exam of 6 pages for the course Atom at Atom (History of the Atom)
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History of the AtomDemocritus - answer Gave us the word "atom"
John Dalton - answer described the atom as a solid sphere
J.J. Thomson - answer Discovered negatively charge particle called electrons;
Describe the atom as blueberry muffin, chocolate chips in a cookie where the
blueberries and chips were the electrons.
Ernest Rutherford - answer Found that atom had a densely packed, POSITIVELY,
charged center in the atom, called the NUCLEUS;
Niels Bohr - answer Discovered that electrons move around the nucleus in orbitals
Atom - answer Basic unit of matter
Nucleus - answer Center of an atom that contains both protons and neutrons
Proton - answer Found in the nucleus of an atom and has a positive charge
Electron - answer Negatively charged particles that orbit the nucleus
Neutron - answer A particle with no charge found in the nucleus
Atomic Number - answer The number of protons in an atom
Atomic Mass - answer The number of protons AND neutrons
Democritus - answer(c. 450 BCE) came up with "Atomos" (uncuttable); all matter made
of small particles that were indivisible
John Dalton - answer(1808) looked at how gases combine chemically; looked at ratios
of how elements combine to form compounds (stoichiometry); saw that elements always
combined in whole number ratios to form compounds; supported idea of atom; billiard
ball model
said 1) all matter is made of indestructible atoms, 2) all atoms of an element are
identical, 3) atoms of different elements have unique properties, 4)atoms combine to
make larger compounds
, Billiard Ball Model - answer by John Dalton; round atoms with no distinguishing
characteristics
J.J. Thompson - answer showed existence of electrons; played with Cathode Ray
Tubes (vacuum tubes filled with a gas); applied electric field and saw a stream of
particles (electrons) move towards positive end; plum pudding model
Plum pudding model - answer Thompson; atoms are blobs of positive charge studded
with electrons
Chadwick - answer found neutrons
Ernest Rutherford - answer(1909) showed that atoms are mostly free space, 1st proof of
protons in a nucleus, electrons are outside nucleus in space; played with radioactivity
and shot alpha particles at Au (Au Foil Experiment, foil fluorescent screen lights up
when alpha particles hit it)
Niels Bohr - answersaid electrons are in orbits with energy levels around the nucleus
(however this only works with H); Planetary Model; played with gas discharge model
Democritus - answer400 BC - All matter is composed of tiny, invisible, and indivisible
particles in motion. He called these particles atoms.
John Dalton - answer1808 - gathered evidence favoring Democritus' theory. Proposed
an Atomic Theory. 1) Every element is made of tiny, unique particles called atoms that
cannot that cannot be subdivided. 2) Atoms of the same element are exactly alike. 3)
Atoms of different elements can join to form molecules.
JJ Thompson - answer1897 - Discovered 1st component of atom (the electron) through
his cathode ray experiment. His model "the plum pudding model" saw an atom as a ball
of positively charged stuff with electrons scattered throughout.
Ernest Rutherford - answer1912 - Discovered through his gold foil experiment that the
atom was mostly empty space. Positive charge is in center of atom (nucleus). Electrons
circle nucleus like planetary obits.
Niels Bohr - answer1913 - His model has a nucleus, but the electrons have certain
energy levels which determine their path around the nucleus. Electrons cannot be found
in between energy levels.
James Chadwick - answer1932 - Discovered the neutron.
aristotle - answersaid matter is infinitely divisible, and that no matter how small a piece
is, it can always be divided into smaller pieces.
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