Basic Structure of the Atom

Nucleus
- The center of the
atom, this contains most of the
mass of the atom and has a
positive charge

Electrons - these contain very
little mass (we'll say none for
simplicity) and circle the atom
in layers that we call shells.
The Nucleus

The nucleus of the atom contains two types of particles.

Protons - These contain a positive charge equal to the
negative charge of the electron and have a mass of 1
AMU
(Atomic Mass Unit)

Neutrons
- These have a neutral charge (no charge) and
have a mass of 1 AMU (Atomic Mass Unit)
Elementary Facts

Elements are made of only
one type of atom

Atomic Number - This is
the number of protons in an
atom.  This is what gives an
atom it's properties.

Mass Number - The total
number of protons and
neutrons in the nucleus.
The picture at the left has
an atomic number of 12 (6
protons and 6 neutrons)

Isotopes - these are atoms
that have a different number
of neutrons than 'normal'.  If
the atom at the left had 7 or
8 neutrons it would still be
Carbon (6 protons) but it
would have a larger mass
number (13 or 14)
Placing
Electrons in
Shells

Only a limited
number of
electrons can fit
in each shell of
an atom.
Shell
# of
Electrons
1
2
2
8
3
8
Remember this
sequence of
numbers.  It will
come in handy for
the next chapter
(hint, hint)
Of course all this begs the question,
"What are Protons, Neutrons and Electrons made of?"  
The answer to this is found in the link below.  
Click it
IF YOU DARE!

Quarks!
Structure of the Atom