Basic Atomic
Structure
What does the atom look like?
Democritus theorized a solid, indestructible object
His atom looked something like this:
It wasn’t until J.J.Thompson
came around, that the theory of
atomic structure changed. Why?
Cool, huh? This was
the primary idea of
the structure of an
atom for almost 2000
years.
The discovery of protons & electrons!!!
The Thompson Model: called the “Plum-pudding”
Model
Scattered
electrons
“Ball” of positive charge,
with electrons randomly
scattered throughout.
Cloud of Positive
charge
Rutherford Model:
With the discovery of the nucleus, Protons are localized in the
center of the atom, and electrons are circled around them.
Bohr Model:
Bohr theorized that
electrons followed
specific pathways
around the nucleus:
called “orbitals”
While this model is probably most familiar…
it STILL isn’t accurate!
The Quantum Mechanical Model:
This model states that
electrons still follow
specific pathways,
these orbitals, have
specific 3D shapes:
It also says that because you
can never know the speed of an
electron & its position at the
same time, you could only guess
where an electron was likely to
be 90% of the time:
What you need to know about:
subatomic particles



Protons- positive charge, in the nucleus,
has a mass of 1 amu
Neutron- neutral/no charge, in the nucleus,
has a mass of 1 amu
Electron- negative charge, towards the
outside of the atom, has no mass