Transcript symbol of radioactivity

CHAPTER 21
NUCLEAR CHEMISTRY
I. Ordinary Chemical Reactions
A. Bond breaking, bond forming, only
outer electrons of the atoms are
disturbed.
B. Nuclei of the atoms are unaffected.
II. Nuclear Reactions
A. Deals with changes in atomic
nuclei.
B. Importance
1. Nuclear reactors - radioactivity
2. Atomic bombs – nuclear fission
(splitting nuclei.
3. Hydrogen bomb – nuclear fusion
(joining nuclei)
II. Review of the nucleus of the atom
A. Composed of nucleons – protons
and ___________ .
B. Each kind of nucleus is called a
nuclide, characterized by its number
of ____________ and number of
______________.
C. Two atoms whose nuclei have the
same no. of protons but a different
no. of neutrons are called _________.
D. The no. of protons is given the
symbol ____.
E. The no. of protons and no. of
____________ is called the
______________ with the symbol __.
F. X is the symbol for the element.
G. Some nuclides:
III. There are two types of nuclear
reactions.
A. Radioactive decay – The process in
which a nucleus spontaneously
disintegrates, giving off __________ .
B. Nuclear bombardment reactions –
Those reactions in which a nucleus is
struck by another nucleus or by a
nuclear _________.
IV. Radioactivity
A. Discovered by Becquerel (1896
B. Photographic plates developed
bright spots when exposed to
____________________ .
C. Later shown to be separable by
electric and magnetic fields into
three types; _______ , _________ ,
and ________________________ .
1. Alpha rays bend away from a
positive plate indicating they are
_______________ . They are known to
consist of helium-4 nuclei.
2. Beta rays bend in the opposite
direction indicating they have a
______________. They consist of
high speed ___________ .
C. Gamma rays – a form of
electromagnetic radiation –
wavelength ~ 10-12m
V. Nuclear equations
A. def. – a symbolic representation of
a nuclear reaction
B. Only nuclei are represented – not
necessary to indicate electron charges
for any ions involved.
D. Reactant and product nuclei are
represented in nuclear equations by
their ______ ________ .
E. Other particles are given the
following symbols:
F. To balance nuclear reactions:
1. Sum of the mass numbers of the
reactants must = the sum of the mass
numbers of the __________ . (A’s)
2. Sum of the atomic numbers
(protons) of the reactants must = the
sum of the atomic numbers of the
_____________ . (Z’s)
An example:
First radioactive element
found by Marie Curie –
naturally decaying Polonium
Notice 84 = 82 + 2 (Z’s) sum of
atomic numbers are equal on both
sides. 212 = 208 + 4 (A’s) equal too.
How would you complete the
following?
How will you identify the symbol for
the element? What is its atomic
number? _____ What is its mass
number?
What is its nuclide symbol? _____
G. Types of radioactive decay –
spontaneous change of unstable
nuclide.
1. Alpha emission – emission of alpha
particle (α)
Parent nuclide
Daughter nuclide
Fill in the blank:
2. Beta emission – β-decay emission
of
Fill in the blank:
3. Positron emission β+ decay
Try this one:
4. Electron capture (EC) – one of the
electrons in an atom is captured by
the nucleus of the atom
Try this one:
5. Gamma ray emission – in many
cases, radioactive decay results in a
daughter nucleus that is in an excited
state; the excited state is unstable and
goes to a lower-energy state by
releasing energ y in the form of
gamma rays.
VI. Nuclear Stability
A. The nucleus of an atom is stable if
it does NOT change into another
nuclide without adding outside
energy.
B. Look at each element, determine
what nuclides of the elements are
stable, plot stable nuclides on graph.
No. of protons x axis
No. of neutrons y-axis
Which one lies on the N=Z line?
C. Band of stability
1. Lighter stable nuclei Z < 20
2. As Z increases ratio increases to
~1.5 ( possible reason, as Z increases,
the repulsion of the protons increases,
and more neutrons are neede to give
attractive nuclear force.
3. No stable nuclides Z > 83, all are
radioactive.