LECTURE-FINAL EXAM Flashcards
denoted by number of protons
Z- atomic number
protons+neutrons
mass number (A)
a positively charged particle,
protons
Z 1 and A 1
symbol
1p1
protons
neutral particle
neutrons
Z=0 A=1 symbol= 1n0
neutrons
negatively charged particle with negligible mass,
electrons
symbol= 0e1
electrons
What determines the nuclear stability
competition between
attractive strong force and repulsive electrostatic force
it is 137 times stronger than the repulsive force but operated only ove rthe short distances within the nucleus
strong force
Electrostatic repulsive forces between protons would break
the nucleus apart if not for the presence of an attractive
force called
strong force
Exists between all nucleons
strong force
consists of protons and neutrons and is found at the center of of all atoms
nucleus
-
all atoms have protons and neutrons in their
respective nucleus except for
Hydrogen
protons and neutrons are generally called
nucleons
*
the study of reactions involving changes in the atomic nuclei
nuclear chemistry
Nuclear chemistry began with the discovery of natural radioactivity by
Antoine Becquerel
It is further developed through the subsequent investigations by Pierre
and Marie Curie and many others
Nuclear chemistry
Applications of nuclear chemistry
nuclear bombs
hydrogen bombs
harnessing nuclear energy through the use of nuclear reactors in nuclear power plants
-
atoms having the same atomic number ( and nearly
identical chemical behavior but with different atomic mass or mass
number ( and different physical properties
Isotopes
radioactivity is also known as
radioactive decay
both are known to as nuclear reactions which differ significantly from ordinary equations
Radioactivity
or Radioactive decay and Nuclear Transmutation
a phenomenon in which an unstable nucleus or nuclide emit
particles and or electromagnetic radiation to form a more stable product
or nuclide
Radioactivity (Radioactive decay)
The decaying reactant or nuclide is called the the product nuclide is called the
parent ; daughter
All elements having an atomic number greater than 83 are
radioactive
N/Z<1
unstable except 1H1 and 3He2
involves the loss of an α particle from a nucleus
For each α particle emitted by the parent, A decreases by 4 and Z
decreases by 2 in the daughter It is the most common means for a
heavy, unstable nucleus to become more stable
alpha decay
Every
element beyond bismuth (Bi Z= 83 is radioactive and
exhibits this decay
a-decay
is a more general class of radioactive decay
B-decay
Results
in a product nuclide with the same A but with Z one
higher (one more proton) than in the reactant nuclide In other
words, an atom of the element with the next higher atomic
number is formed
B- decay (negatron emission)
occurs through a
process in which a proton in the nucleus is converted into a
neutron, and a positron is expelled
β+ emission (Positron emission)
has the opposite effect of β- decay the
daughter has the same A but Z is one lower (one fewer proton)
than the parent Thus, an atom of the element with the next lower
atomic number forms
β+ emission (Positron emission)
involves the radiation of high energy γ
photons from an excited nucleus and usually accompanies many
other (but mostly β types of decay
Gamma (γ) Emission
Because
rays have no mass or charge, emission does not
change A or Z
A parent nuclide may undergo
a series of decay steps before
a stable daughter nuclide
forms. The succession of steps
decay series/disintegration series
typically depicted on a grid like
display.
decay series/disintegration series
nuclides with too many neutrons for
stability (a high N Z lie above the band of stability They undergo
β decay, which converts a neutron into a proton, thus reducing the
value of N/Z
neutron rich nuclides
nuclides with too many protons for stability
(a low N Z lie below the band They undergo β decay (lighter
elements) and e capture (heavier elements)
proton rich nuclides
Nuclides with Z 83 are too heavy to be stable
and undergo α decay which reduces their Z and N values by two
units per emission
heavy nuclides
another type of radioactivity resulting from the bombardment of
nuclei by neutrons, protons, or other nuclei Occurs naturally in
outer space but could also be achieved artificially
nuclear transmutation
conversion of atmospheric nitrogen to carbon-14 and 1H1 through the capture of neutron from the sun
nuclear transmutation
occurs when the nucleus interacts with an electron in an
orbital from a low atomic energy level The net effect is
that a proton is transformed into a neutron
electron capture
are massive and highly charged, which
means that they interact with matter most
strongly of the three common types of
emissions
a particles
*
penetrate so little that a piece of paper,
light clothing, or the outer layer of skin can
stop α radiation from an external source
a particles
*
Even though a given particle has less chance
of causing ionization, a β –(or β emitter is a
more destructive external source because the
particles penetrate deeper Specialized heavy
clothing or a thick 0 5 cm) piece of metal is
required to stop these particles
B- particles
*
have less charge and much less mass than α
particles, so they interact less strongly with
matter
B- particles
*
neutral, massless γ rays interact least with
matter and, thus, penetrate most A block
of lead several inches thick is needed to
stop them Therefore, an external γ ray
source is the most dangerous because the
energy can ionize many layers of living
tissue
y- particles
TRUE or FALSE
Isotopes of an element exhibit very similar chemical and physical
behavior
TRUE
SI unit for radioactivity is ________ and defined as ________
Becquerel= d/s
Curie is a commonly used unit ad 1Ci is equivalent to
3.70x10^10 d/s
TRUE or FALSE
For a large collection of radioactive nuclei, the number decaying per unit
time is proportional to the number present
TRUE
is the time it takes for half the nuclei present in a sample
to decay
Half life of Radioactive Decay (t 1/2
TRUE or FALSE
The half life of a nuclear reaction can be determined
from its rate constant
TRUE
TRUE or FALSE
This half life is dependent on the number of nuclei
and is inversely related to the decay constant
FALSE
This half life is not dependent on the number of nuclei
and is inversely related to the decay constant
uses radioisotopes to determine the age of an
object
*
Radioisotopic Dating
discovered by the American chemist Willard F
Libby (Nobel Prize in Chemistry in 1960 and is based on
measuring the amounts of 14 C and 12 C in materials of
biological origin
Radiocarbon Dating
is the energy required to break 1 mol of atoms into
neutrons and hydrogen atoms, which equals the energy
to break 1 mol of nuclei into individual nucleons
Nuclear Binding Energy
the energy an electron acquires when
it moves through a potential difference of 1 volt
electron
volt (eV)
1eV = ? J
1.602x10^-19J
1MeV= ? eV
10^6 eV
1 amu = ? eV = ? MeV
931.5 x 10^6 eV = 931.5 MeV
The total quantity of mass energy in the universe is
constant (Law of Mass and Energy Conservation)
when any reacting system releases or absorbs
energy, it also
loses or gains mass
In order to harness the energy of nuclear fission, much of which
eventually appears as heat, is by means of a
chain reaction
example of uncontrolled fission
atomic bomb
example of controlled fission
nuclear reactors
used as a nuclear fuel and produced
in breeder reactors, is one of the most toxic substances
known It is an alpha emitter with a half life of 24 400 yr (Production of nuclear waste)
Plutonium-239
is the ultimate source of nearly all the
energy on Earth because almost all
other sources depend, directly or
indirectly, on the energy produced by
nuclear fusion in the Sun
Nuclear fusion
*
All the elements larger than
hydrogen were formed in
fusion and decay processes within stars
holds great promise as a source of clean
abundant energy, but it requires extremely high temperatures
and is not yet practical
nuclear fusion
Requires enormous energy in the form of heat to give the
positively charged nuclei enough kinetic energy to force
themselves together
nuclear fusion
Promising and may represent an ideal source of power
nuclear fusion
Types of solids
- crystalline solid
- amorphous solid
possesses rigid and long-range order. In a crystalline solid, atoms, molecules or ions occupy specific (predictable) positions.
crystalline solid
does not possess a well-defined arrangement and long-range molecular order.
amorphous solid
an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing
glass
types of crystals
- ionic crystals
- covalent crystals
- molecular crystals
- metallic crystals
an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing
glass
-Lattice points occupied by cations and anions
-Held together by electrostatic attraction
-Hard, brittle, high melting point
-Poor conductor of heat and electricity
ionic crystals
-Lattice points occupied by atoms
-Held together by covalent bonds
-Hard, high melting point
-Poor conductor of heat and electricity
covalent crystals
Lattice points occupied by molecules
-Held together by intermolecular forces
-Soft, low melting point
-Poor conductor of heat and electricity
molecular crystals
-Lattice points occupied by metal atoms
-Held together by metallic bonds
-Soft to hard, low to high melting point
-Good conductors of heat and electricity
Metallic Crystals
the basic repeating structural unit of a crystalline solid.
unit cell
types of unit cells
Simple cubic
Tetragonal
orthorhombic
rhombohedral
monocyclic
triclinic
hexagonal
Types of cubic cells
Simple cubic
Body-centered
face-centered cubic
Simple cubic
1 atom/unit cell
body-centered cubic
2 atoms/ unit cell
face-centered cubic
4 atoms/ unit cell
Chemical reaction/ Nuclear reaction
one substance is converted into another, but atoms never change identity
Chemical reaction
Chemical reaction/ Nuclear reaction
Orbital electrons are involved as bonds break and form; nuclear particles do not take part
Chemical reaction
Chemical reaction/ Nuclear reaction
Reactions are accompanied by relatively small changes in energy and no measurable changes in mass
Chemical reaction
Chemical reaction/ Nuclear reaction
Reaction rates depend on number of nuclei, but are not affected by temp, catalysts, or except on rare occasions, the compound in which an element occurs
Nuclear reaction
Chemical reaction/ Nuclear reaction
Protons, neutrons, and other particles are involved; orbital electrons take part much less often
Nuclear reaction
Chemical reaction/ Nuclear reaction
reaction rates ar einfluenced by temp, conc, catalysts and the compound in which an element occurs
chemical reactions
Chemical reaction/ Nuclear reaction
atoms of one element typically are converted into atom of another element
Nuclear reaction
Chemical reaction/ Nuclear reaction
Reactions are accompanied by relatively large changes in energy and measurable changes in mass
Nuclear reaction
