Atomic History Chemistry Democritus , Dalton , JJ Thomson, Rutherford , Schrodinger

All about the history if atoms

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ATOMIC HISTORY
CHEMISTRY 1-2
Period - 2
10/2/24

2. Democritus 400 BC

1.He believed that all matter is composed of
tiny, indivisible particles called "atoms"
which are indestructible, always in motion,
and differentiated by their shape and size
2.The word "atom" comes from the Greek
word “atomos”
3.Indestructible: Democritus believed atoms
cannot be destroyed.
4.Infinite variety: He thought there are an
infinite number of atoms with different
shapes and sizes.

3. John Dalton 1808
1) The first part of his theory states that all matter
is made of atoms, which are indivisible. The second
part of the theory says all atoms of a given
element are identical in mass and properties. The
third part says compounds are combinations of two
or more different types of atoms.
2) The key difference between his Atomic Theory
and the ideas of Democritus was that he based his
theory on experimental evidence and observations
3) He was correct in the matter that the atom is
the smallest known particle that can take part in a
chemical reaction.

4. JJ Thomson 1897
1)A cathode ray is a beam of electrons in a
vacuum tube traveling from the negatively
charged electrode (cathode) at one end to the
positively charged electrode (anode) at the
other, across a voltage difference between the
electrodes. They are also called electron beams.
2) He conducted experiments with cathode rays
and concluded that they consisted of negatively
charged particles, which we now know as
electrons.

5. Ernest Rutherford 1911
1) A piece of gold foil was hit with
alpha particles, which have a positive
charge. Most alpha particles went
right through. This showed that the
gold atoms were mostly empty space.

2) Rutherford's model proposed that
the negatively charged electrons
surround the nucleus of an atom.

6. Niels Bohr 1913
1) The Bohr model postulates that
electrons orbit the nucleus at fixed energy
levels.

2) The Bohr Model is known as a planetary
model because these orbits look similar to
that of planets orbiting the sun. Electrons
orbit around the nucleus because of the
electrostatic attraction between their
negative charge and the positive charge of
the protons within the nucleus

7. Niels Bohr 1926
1) The Schrödinger model assumes
that the electron is a wave and tries to
describe the regions in space, or
orbitals, where electrons are most
likely to be found.
2) The electron cloud model shows a
particular area in which an electron is
likely to be.