Atomic Models

Atomic Models

LO recognize different types of atom models
Key words
Atom
Nucleus
Electron
Proton
Neutron
Electron cloud

Identify the three types of subatomic particles?

Dalton’s Atomic Theory
• Matter is composed of extremely small particles called atoms.
• Atoms are indivisible and indestructible.
• Atoms of a given element are identical in size, mass, and
chemical properties.
• Atoms of a specific element are different from those of another
element.
• Different atoms combine in simple whole-number ratios to form
compounds.
• In a chemical reaction, atoms are separated, combined, or
rearranged.

400 b.c. Democritus Model
elements consisted of tiny, solid particles that could not be
subdivided.
particles named atomos, “uncuttable.”
Democritus’s atomic theory was rejected.

1904 Thomson Model
a spherical atom containing
small, negatively charged
particles.
He thought these “electrons”
like chocolate chips in a ball of
cookie dough.

1911 Rutherford Model
all the positive charge of an atom was concentrated
in a central atomic nucleus that was surrounded by
electrons.

1913 Bohr Model
electrons traveled in fixed orbits,
The electrons could jump between orbits as they absorbed
or released energy.
The model worked for hydrogen, but did not work for atoms
with many electrons.

The electron cloud model1926
An electron cloud is the area around the nucleus
electron is smaller in mass than proton or neutron.

Explain the difference between the Bohr
model and the electron cloud model.