I can describe atoms.
atoms.
Warm Up 10/17
Which scientist proposed each model of the
atom represented by the images below?
Modern Models of Atoms
Niels Bohr
Bohr’s Model
The atom is made of a dense positively charged
nucleus and electrons that orbit it.
Niels Bohr created a model of the atom that
helped explain the motion of electrons and
other phenomena that had been observed.
The more energy an electron has the further
from the nucleus it orbits.
Only certain energies are allowed.
Bohr’s Model
Electron Cloud Model
Each energy level of an atom has a maximum
number of electrons that it can hold.
As new information became available the model
of the atom was improved.
The higher the energy level the more electrons
it can hold.
We have learned that electron energy levels are
not spherical like Bohr assumed.
2nd level: 8 e1st level: 2 eLower energy levels typically fill up first.
We also cannot know exactly where an atom is,
only where it is likely to be.
Electron Cloud
The electron cloud is denser where electrons are
most likely to be.
Scientists (and Philosopher)
Scientist
(philosopher)
Experiment
Democritus
Subatomic particles are particles that are
smaller than an atom.
Three subatomic particles are found within
atoms.
Particle
Symbol
Mass
(amu)
Charge Location
Idea/name of atoms
Dalton
Compared masses of
elements in compounds
Evidence for the existence of atoms
Thomson
Cathode-ray tube
deflection
Atoms contain smaller negatively
charged particles called electrons
Rutherford
Alpha particles through
Gold foil
Most of the mass of an atom is in a small
but dense, positively charged nucleus
Bohr
Subatomic Particles
Result / Big Idea
Electrons can only exist in certain
orbits/energies