2. Particles in the Atom Electrons
(-) charge no mass located outside the nucleus
Protons
(+) charge amu located inside the nucleus
Neutrons
no charge amu located inside the nucleus
Atom – the smallest unit of an element that retains its chemical properties.
Atoms can be split into smaller parts.

3. Lame Jokes Two atoms are walking down the street.
One atom says to the other, “Hey! I think I lost an electron!”
The other says, “Are you sure??”
“Yes, I’m positive!”
A neutron walks into a restaurant and orders a couple
of drinks. As she is about to leave, she asks the waiter
how much she owes. The waiter replies, “For you,
No Charge!!!”

4. Subatomic particles Actual e- -1 p+ +1 no mass (g) Relative mass Name
Symbol
Charge
Electron e- -1
1/1840
9.11 x 10-28
Proton p+ +1 1
1.67 x 10-24
Neutron no 1
1.67 x 10-24

5. Structure of the Atom There are two regions Electron cloud The nucleus
With protons and neutrons
Positive charge
Almost all the mass
Electron cloud
Most of the volume of an atom
The region where the electron can be found

6. Subatomic Particles equal in a neutral atom Atomic Number
NUCLEUS
ELECTRONS
equal in a neutral atom
PROTONS
NEUTRONS
Negative Charge
QUARKS
Atomic Number
equals the # of...
Positive
Charge
Neutral
Charge
Most of the atom’s mass.
Courtesy Christy Johannesson

7. Counting the Pieces C Atomic Number = number of protons12 6 C 14 6 C
Mass Number = A
Atomic Number = number of protons
# of protons determines kind of atom
Atomic Number = number of electrons in a neutral atom
Mass Number = the number of protons + neutrons C 12 6
Atomic Number = Z
California WEB

8. Isotopes:
different varieties of an element’s atoms --
have diff. #’s of n0; thus, diff. masses --
some are radioactive; others aren’t
All atoms of an element react the same, chemically.
Isotope
Mass p+ n0
Common Name
H–1 1 1
protium
H–2 2 1 1
deuterium
H–3 3 1 2
tritium
C–12 atoms
C–14 atoms
6 p+
6 n0
6 p+
8 n0
stable
radioactive