SCH3U Isotopes, Average Atomic Mass and Radiometric Dating 2014
Name: ____________________________________
Knowledge
A.
B.
Inquiry
Date: ___________________________
Communication
Applications
The Development of Atomic Theory. (Refer to pages 14-16 for Mendeleev,
Döbereiner, page 27 for Soddy and pages 24-25 for Bohr and Rutherford).
A
Scientist
Mendeleev
B
Soddy
C
Bohr
D
Döbereiner
E
Rutherford
Work
The first scientist to see trends in the physical properties of
elements and grouped them into triads (ex Li, K & Na)
Used the Gold Foil experiment to determine that atoms have very
tiny, positively charged nuclei
Discovered that atoms could have varying numbers of protons and
coined the term “isotope”
Used spectroscopy experiments to determine the energy levels
and electron arrangement of atoms
Created the first periodic table – using physical properties to place
elements into groups and ordering elements by atomic mass.
Atomic data
1. Complete this table:
symbol
1
1H
2
1H
4
2He
7
3Li
18
8O
p+1
n0
e-1
symbol
39
19K
88
38Sr
235
92U
239
94Pu
37
17Cl
p+1
n0
e-1
2. Give the numbers of neutrons, protons, and electrons in the atoms of each of the
following isotopes:
a) Carbon-14
b)
Radium-222
c)
Uranium-238
d)
Iodine-131
3. Write the symbols of the isotopes that contain the following.
a) An isotope of silver whose atoms have 63 neutrons
b) An isotope of cobalt whose atoms have 33 neutrons
c) An isotope of strontium whose atoms have 62 neutrons
d) An isotope of oxygen whose atoms have 8 neutrons
1
C.
Periodic table
term
A group
B
C
E
Noble gases
Representative
elements
Alkali Earth
Metals
Actinides
F
Period
G
H
Lanthanides
Alkali Metal
I
Transition
elements
Halogen
D
J
D.
E.
Terminology
term
A Alpha (α) particle
B Mass spectrometer
C Valence electron
D
Atomic mass
E
F
G
H
fission
Atomic number
Half-life
SATP
I
J
radioisotope
Beta (β) particle
Definition
d-block elements that are all metals. They are often multivalent and are found in the “B” columns in the periodic table
Very reactive non-metallic elements in column 17
Non-reactive gases found in column 18. These elements
have filled valence shells
Inner transition elements with atomic numbers between 89
and 102 (if heavier than U, called a trans-uranic element)
Elements found in the “A” columns in the periodic table .
they have easily determined ionic charges.
Elements that are silvery, soft, very reactive, one outer shell
electron
A row going across the periodic table
Inner transition elements with atomic numbers between 57
and 71 (also called rare earth elements)
Elements that are silvery, brittle, reactive, two outer shell
electrons
A column going down the periodic table
definition
The number of protons in an atom
25°C and 100 kPa
An unstable isotope of an element capable of emitting
particles or radiation
The time it takes for one half of the nuclei in a
radioactive sample to decay
Electrons that occupy the outer orbital shell of an atom
A helium nuclei (42He2+)
A high energy electron
Splitting of a large nucleus into small nuclei (occurs in
the reactor of nuclear power plants)
The number of protons and neutrons in an atom
A device used to determine the mass of particles (ex.
Isotopes)
Average Atomic mass
1. Natural lithium comes in only two isotopes of Li-6 (7.42%) and Li-7 (92.58%). Determine
the average atomic mass for Lithium.
2. Calculate the relative atomic mass of gallium given that the relative abundance of its
two isotopes are: 60.5% of Ga-69 and 39.5% of Ga-71.
2
3. Oxygen occurs as one major isotope and two minor isotopes. O-16 (99.759%), O-17
(0.037%) and O-18 (0.204%). Calculate the average atomic mass of oxygen.
4. Iron has four isotopes; Fe-54 (5.82%); Fe-56 (91.66%); Fe-57 (2.19%) and Fe-58 (0.33%).
Determine the average atomic mass for natural iron.
5. Nickel has five naturally occurring isotopes. We will exclude all the special isotopes
synthetically made in nuclear reactors. The isotopes are:
Ni-58 67.88%
Ni-60 26.23%
Ni-61 1.19% Ni-62 3.66% Ni-64 1.08%
Calculate the average atomic mass of nickel
6. Iridium (a metal rather like platinum) occurs with only two isotopes of mass number 191
and 193. The atomic weight of iridium is 192.2. Deduce the relative abundance of the
two isotopes of this element.
F.
Radioisotope Decay Equations.
1. Write an equation for the β-decay of 8737Rb.
2. Write an equation for the α-decay of Pu-239.
3. Write an equation for the α -decay of 146C.
G.
Radiometric Dating Questions
1. How do you manage to absorb C-14 into your body?
2. When a rock solidifies from magma, it contains a large amount of the mineral
Orthoclase (KAlSi3O8). 0.0117% of all K atoms are the isotope K-40 which is radioactive
and undergoes β-decay. Write a β-decay equation for K-40. K-40 has a half-life of 1.277
billion years? A sample of Orthoclase contained 12.48 mg of K-40 when it formed.
Today the sample contains 3.12 mg of K-40. What is the age of the sample of
Orthocalse?
3. A Woolly Mammath is found frozen in the Siberian Tundra. The normal ratio of 14C to
12
C is 1.046 ppt (parts per trillion). The 14C/12C ratio in the Mammoth is 0.131 ppt. 14C
has a half-life of 5730 years. What is the age of the mammoth?
H.
Nuclear Power
1. Explain in a series of steps how Nuclear Electric Energy is produced.
2. List 3 advantages and 3 disadvantages of Nuclear Power.
3