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Quantum
Nuclear
A nuclear reaction is when the particles of an atom change. All elements that are larger
than Bismuth (with some exceptions) have radioactivity and will decay into smaller
elements. These reactions can result into different isotopes and even different atoms
when these reactions occur.
Nuclear reaction
Type
Description
Alpha
Helium
this is a type of atomic fission (when atoms
split into two parts); it is really just the
nucleus of a helium atom without any
electrons; the mass of the atom changes by
four and the number changes by two
electron
this is the emission of an electrons from the
nucleus; it results in the conversion of a
neutron to a proton; when the neutron to
proton ratio is too high
Similar to electron
but a positive
charge
this is the emission a particle like an
electron but with a positive charge: a
positron; it results in the the conversion of
a proton into a neutron; neutron to proton
ratio is too low
No charge
this is the emission of a photon (a particle
of light) with a very high energy; it has no
effect on the nucleus and is simply the
release of energy; gamma rays are emitted
Beta
Positron
Gamma
Neutron
neutrons can be emitted as part of a nuclear
fission process in which a single nucleus
splits into smaller nuclei
Electron Capture
this process occurs when an electron is
absorbed by the nucleus; the electron so
‘captured’ combines with a proton to
produce a neutron
electron
Half-life
This the amount of time for ½ of atoms in a radioactive isotope to decay. The equation
for a first order reaction is .693/k where k is a rate constant. The stoicheometric
equation is final amount equals the initial amount time (1/2)^(time passed/ half life
time) or
Energy created Reactions
1. Nuclear fission: reactions in which an atom's nucleus splits into smaller parts,
releasing a large amount of concentrated energy in the process. Experimentally this is
done with the addition of a neutron. The atom then splits into two atoms releasing high
energy gamma rays that can be harnessed in nuclear reactors.
2. Nuclear fusion: The inverse of what occurs in fission. The atoms combine to form a
larger atom. A good example is the fusion of unstable hydrogen isotopes of hydrogen
(deuterium: H2 and tritium: H3) into the element helium. Nuclear fussion is highly
impractical because of the energy needed to start the reaction. This usually takes place
on the surface of the sun and future search is being done on the concept of cold fusion.
These reactions are called thermonuclear reactions because of the heat given off when
applied.
Quantum Numbers
• The principal quantum number is the energy level which an electron of a certain
atom can occupy
• The angular quantum number is the sublevel it can occupy where 0 is the s
subshell. p=1 and so on. This is always 1 minus the principal number
• The magnetic quantum number +or – the angular number representing the orbital
in the sub shell that the electron occupies
• The spin quantum number is + or - ½ because electrons cannot have the same
spin in an orbital
Geometry tables
Bonding
Lone
Electron
Electron
Pairs Domains
Pairs
2
0
2
Shape
linear
Ideal Bond Angle
(example's bond Example Image
angle)
180°
CO2
trigonal
planar
bent
tetrahedral
trigonal
pyramidal
bent
trigonal
bipyramidal
3
0
3
120°
BF3
2
4
1
0
3
4
120° (119°)
109.5°
SO2
CH4
3
1
4
109.5° (107.5°)
NH3
2
2
4
109.5° (104.5°)
H2O
5
0
5
90°, 120°
PCl5
4
1
5
seesaw
3
2
5
T-shaped
2
3
5
linear
180°
XeF2
6
0
6
octahedral
90°
SF6
5
1
6
square
pyramidal
90° (84.8°)
BrF5
4
2
6
square planar
90°
XeF4
7
0
7
pentagonal
bipyramidal
90°, 72°
IF7
180°, 120°
(173.1°, 101.6°)
90°, 180° (87.5°, <
180°)
SF4
ClF3
Molecular Orbital Theory
Molecular Orbital theory gives a model of the likeliness to form separate electron clouds
(antibonding) or when the electron clouds form together (bonding)
Definitions
Diamagnetism- no permanent dipole moments no unpaired orbitals
Paramagnetism- A paramagnetic material is one with unpaired electrons which orient
their spins temporarily in the direction of an applied magnetic field and is thus attracted
slightly to any magnet but cannot be magnetized itself.
Ferromagnetism- A ferromagnetic material is one with unpaired electrons whose spins
will line up permanently after a sufficiently strong magnetic field is applied, thus
becoming a permanent magnet, and is also attracted strongly to any magnet, even if the
field isn't strong enough to magnetize it.
The Aufbau principle states that orbitals are filled starting with the lowest energy
The Pauli exclusion principle states that the maximum number of electrons occupying an
orbital is two having opposite spins
Hund's rule states that when there are several MO's with equal energy the electrons fill
one MO at a time.
Orbital- a specific region of an atom where there is a high likeliness that an electron will
actually be
s orbitals are sphere like
p are dumbbell like
d,f, and so on have more complicated structures
For bonding to exist the bond order defined as:
must have the value of 1 or higher.
Hybridization of Molecules
When atoms are forming bond the orbitals of the sub shells can fuse to form hybrid
orbitals. These orbitals show characteristics of both subshells. The hybridization is
largely determined by the amount of bonds that the atom has. When forming double
bonds the orbitals are removed out of hybridization to form a pi bond. Hybrid orbitals
determine the shape of the molecules. The principle theory behind hybrid orbitals is to
create the greatest amount of space. Lone pairs will change the angles of the molecule
because of valence shell electron pair repulsion where the negativity of the electron pair
will repel all like charged bonds.