Transcript Document

-Different FORMS of an Element that occur Naturally
-Have the SAME # of P and E but DIFFERENT # of N
-Isotopes of an element have the SAME CHEMICAL
PROPERTIES
ATOMIC MASS
12
6
C
N = 12 -6 = 6
C
ATOMIC #
14
6
N = 14-6 = 8
- Average Mass of all ISOTOPES of
an element
Average Atomic Mass = Isotope Mass + Isotope Mass
# of Isotopes
- Contains PROTONS and NEUTRONS
- Is extremely TINY compared to the size of the atom
- Has most of the MASS of the atom
If PROTONS are POSTIVE, and LIKE CHARGES REPEL, why
don’t PROTONS REPEL EACH OTHER? What keeps them in
the NUCLEUS?
THE ELECTRIC FORCE
THE STRONG FORCE
-Keeps Protons and Neutrons
stuck together
-Force than makes like
charges repel
-100X larger than electric
force
-Makes Protons repel each
other
-SHORT-RANGE force =
quickly becomes weak as
distance between P and N
increases
-LONG-RANGE force = strong
force even when Protons are
far apart
As NUCLEUS SIZE INCREASES:
-STRONG FORCE stays about the SAME
-ELECTRIC FORCE becomes GREATER
LARGE NUCLEUS IS NOT HELD TOGETHER AS
TIGHTLY!
STABLE Nucleus = Strong Force can hold
the nucleus together permanently
UNSTABLE (LARGE) Nucleus = Strong
Force isn’t large enough to hold the
nucleus together tightly
UNSTABLE NUCLEUS = DECAYS (breaks
apart) giving off matter and energy =
RADIOACTIVITY
Nucleus Stability depends on the
RATIO of NEUTRONS to
PROTONS
Nuclei with TOO MANY or TOO FEW
Neutrons compared to Protons =
RADIOACTIVE
Small Nucleus = 1 Neutron :1 Proton ratio for stability
Large Nucleus = 3 Neutrons : 2 Protons for stability
The Heat/Energy released by DECAY
3 Types: 1. Alpha
2. Beta
3. Gamma
-Made of 2 Protons and 2 Neutrons
4
He
2
-Are the same as a HELIUM NUCLEUS
-Have an Electric Charge (2 +)
- Least PENETRATING form of radiation
= can be stopped by a sheet of paper
- Can damage human cells
- More MASSIVE than Beta or Gamma
- The changing of one element into
another through decay
(ADD to CHART)
Alpha particles = element looses 2
protons/2 Neutrons
The NEW ELEMENT:
New atomic # is 2 LESS
New mass # is 4 LESS
-Neutron decays into a PROTON and
emits an ELECTRON (Beta particle)
- Faster and MORE penetrating than
alpha
- Stopped by aluminum foil
- Can damage human cells
- New elements atomic number is
increased by 1
- New elements mass is the same
-Not particles, they are WAVES
-Emitted during Alpha and Beta Decay
-MOST PENETRATING radiation
-Have HIGH FREQUENCIES/SHORTEST
WAVELENGTHS
-No mass, no charge, travel at the speed of
light
-Need thick blankets of LEAD/concrete to
stop them
- Cause LESS damage to human cells
-Amount of time it takes for
1/2 of a radioactive nucleus
to decay to a stable isotope
-Stable isotopes left after
the decay = DAUGHTER
ISOTOPE
-Half-life is different for
different elements
-Using half-lives to determine the age of
materials
1: Compare the amount of Radioactive
Isotope to the amount of Daughter
Isotope in the sample
2. Calculate the # of half-lives
3. # of Half-lives = Age of the material
Ex: Carbon Dating = C-14 = 5,730 years = plant/animals
Uranium Dating = Rocks