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The atom
The building blocks of life.
The insides consists of Protons & Neutrons
The outside consists of Electrons which are
continuously moving.
For the most part:
#e- = #p+
mp = 1.672 614x10-27 kg or 1.007 276 u
mn = 1.674 920x10-27 kg or 1.008 665 u
mp = 9.110 x10-31 kg or 0.000 549 u
u = The atomic mass unit is based on a neutral atom of carbon-12, 6p+ & 6no,
which is given a mass of exactly 12.000 000u
The Bohr-Rutherford model of an atom
Shell
number
1
2
3
4
Max # of
electrons
2
8
18
32
- Electrons are found in shells.
- each shell has a maximum
number of allowable electrons.
-The atom is in a GROUND
STATE when all the electrons are
"where they are suppose to be
normally."
The Bohr-Rutherford model of an atom
- Electrons are found in shells.
- each shell has a maximum number of allowable
electrons.
-The atom is in an EXCITED STATE when an electron
absorbed some energy and jumped into a new shell.
Yet something interesting happens as the
electron travels from energy level to energy
level.
If an electron is EXCITED, that means
energy is ABSORBED and therefore a
PHOTON is absorbed.
If an electron is DE-EXCITED, that means
energy is RELEASED and therefore a
photon is released.
We call these leaps from energy level to energy level QUANTUM
LEAPS.
Since a PHOTON is emitted that means that it MUST have a certain
wavelength.
These photons are part of the electromagnetic spectrum.
They behave as particles of light, and each element will absorb
and emit energy based on their atomic structure.
So what is the takeaway from this...?
Atoms can emit particles. Some times they are the
loosely connected electrons, sometimes they are
photons, and sometimes they are the bits and pieces
from the inside of the nucleus.
Either way, it is known as
RADIOACTIVITY
In 1896 Henri Becquerel found that a sample of uranium
he was doing experiments with had a special property.
After he was done with a series of experiments using the
uranium, he put it into a drawer with a photographic plate.
A photographic plate is a piece of glass covered in
chemicals. It was used as the “film” in old style cameras.
• Becquerel was surprised to find out later that the uranium had caused the plate
to be fogged up, as if it had been exposed to light.
• He correctly assumed that the uranium was emitting radiation similar to visible
light.
The term radioactivity was coined
from Marie & Pierre Curie in their
study of the mineral pitchblend.
Marie come up with the hypothesis
that some particles actually
disintegrate from inside the nucleus.
Before we go further... recap
Standard Atomic Notation
Atomic Number
Atomic # = # of protons = 17
Mass # = Average mass of p+ + n0 = 35 atomic mass units (amu or just u)
To find the neutrons = mass# - atomic# = 35 - 17 = 18
are atoms of the same element that have the
same atomic number but different atomic masses due to
a change in its number of
Abundance - The specific amount of one type of isotope.
The masses on your periodic table (e.g. carbon is 12.01u) are weighted
averages based on the natural abundances.
- Since most carbon is carbon-12, the number is pretty close to 12u.
- But, the little bit of carbon-13 does pull up the number a bit, so we get 12.01u.
- The number of neutrons strongly affects the stability of the nucleus. This is why
some isotopes are more common than others.
- Because different isotopes have different masses, they can be separated from
each other using a mass spectrometer.
-Depending on the mass of the isotope, it will have a specific radius as it
travels through a magnetic field.
Unstable Isotopes
spontaneously disintegrate
out of the
@ Montréal
Nuclear Decay - radiation.
AKA
Nuclear transmutation
-the conversion of one chemical element
or an isotope into another.
Types of Radiation
Three types of radiation were identified.
these alpha particles have the same makeup as the
are emitted at high speeds
have the lowest penetration power - up to 2 cm in air
-results in the original nucleus changing - atomic mass
Alpha decay can occur with larger nuclei.
or
Parent
Alpha
Helium ion
Below is a list of some alpha eming radioacve isotopes.
toxic lead in dried paint samples and in thickness gauges.
is used to inspect luggage for explosives, in
moisture gauges and to locate water and oil-bearing layers in oil
glazes and glassware
helps fluorescent lights last longer.
americium-241. This isotope emits particles, which ionize air
molecules between two metal plates within the smoke detector.
a negative charge. The plates attract the ions, so a small
current flows between the plates.
detector, they absorb some of the
particles. So, the alpha radiation
ionizes fewer air molecules and the
current between the metal plates
decreases. This drop in current
triggers the alarm circuit in the
are electrons (or positrons) that are emitted from beta decay
are deflected greatly in an electric or magnetic field
they travel at various speeds, sometimes approaching the speed of light
can penetrate several centimeters of aluminum
results in the original nucleus changing - atomic mass
and atomic number
inside the nucleus and emits an
- Protron decays into a neutron inside the nucleus and emits a positron
electron
positron
Beta Decay
- A neutron in the nucleus transforms into a proton, electron,
and an extremely small neutral parcle known as anneutrino.
- Charge is conserved because
the charge on the new proton
balances the charge on the
electron emi$ed from the
nucleus.
- Neutrinos are similar to the
more familiar electron, with one
crucial difference: neutrinos do
not carry electric charge.
Parent
Beta particle
electron
current surge protectors in electronic devices.
Promethium-147
Stronum-90
Techneum-99
What is the neutrino?
Since the daughter nucleus has vastly more mass than an electron,
there is practically no recoil of the daughter nucleus during beta decay.
electron emitted by the nucleus.
However, measurements found that most electrons emitted during beta
seemed to just disappear!
In 1930, the Austrian physicist Wolfgang Pauli (1900–1958)
suggested that the missing energy in beta decay was carried away
by a tiny, as-yet undiscovered neutral particle, now called the
neutrino,
Indeed, it was 1956 before an experiment using the intense
radiation at a nuclear power plant finally proved conclusively that
neutrinos actually exist.
opposite to the neutrino.
Transmutation
Decay series of U-238: graphically
Gamma Rays
highest penetration power - 2 km in air
can penetrate a minimum of 30 cm of lead
when these rays are
emitted
Travels at the Speed of Light
No Charge
- nucleus does not change
Often omitted in the equations. The
primary concern being the particles
created.
Does not turn you into the Hulk
Neutron Radiation
Type
Ra
Beta
Beta