Download Atomic Structure and Models

Atoms
Atomic Structure and
Models
I. About Atoms
A.
B.
C.
Atoms are the building blocks of matter.
Atoms are so small and numerous that
we need to use indirect evidence to
study them.
The number of parts that each atom has
determines its chemical properties.
II. Dalton’s Atomic Theory
1.
2.
3.
4.
5.
All matter is made of atoms.
Atoms of the same element are the
same.
Atoms of different elements are different.
Atoms combine to make molecules of
compounds.
Atoms cannot be created or destroyed
(by physical or chemical processes).
III. Parts of Atoms
A.
Protons
1.
2.
3.
B.
Located in the nucleus (central part of the atom)
Have a mass of 1 atomic mass unit (amu)
Have a positive charge
Neutrons
1.
2.
3.
Located in the nucleus
Have a mass of 1 amu
Have no charge (neutral)
(Parts of atoms continued)
C.
Electrons
Located outside of the nucleus
Have a mass of 0 amu
1.
2.
(actually 0.00055 amu but it’s so small that we
ignore it)
3.
Have a negative charge
IV. Models of atoms
A.
Discoveries about atoms have changed
how we picture atoms.
V. Periodic Table & Atoms
A.
B.
C.
The Atomic number tells us how many
protons are in an atom of a certain
element.
The Atomic number also tells us how
many electrons are in a neutral atom.
The Atomic mass is the total (on
average) of the protons + the neutrons.
“2 Rules to Remember”
Atomic # = protons = electrons
Atomic mass = protons + neutrons
VI. Rule Breakers
A.
Ions
1.
2.
3.
4.
5.
Ions have lost or gained electrons.
They no longer have the same number of
electrons as protons.
Only the electron number can change
(remember the electrons are on the
outside)
This means they have a net charge.
Opposite charges attract, forming bonds
between atoms.
Rule Breakers (cont.)
B. Isotopes
1.
2.
3.
4.
Atoms of the same element can
sometimes have extra or fewer neutrons
than average.
These different forms or weights of atoms
are called isotopes.
Isotopes that are heavier or lighter than
“normal” can be radioactive.
Radioactive atoms have nuclei that can
change and give off energy in the
process.