Isotopes or Not?
In each of the following statements, you are given a pair of elements and important information about each. Use this
information to determine if the pair of elements are isotopes or different elements. Keep in mind the the number of protons
tells you the atomic number, and that by adding the number of protons and neutrons gets you the atomic mass. If the atomic
mass you see after adding the protons and neutrons together doesn’t match the periodic table mass, it is an isotope. (You will
need a Periodic Table and see your notes and page 175 - 177)
Once you have determined that an given element is an atom or an isotope, write beside each one the results of
your findings. For example:
A. Sample A has 3 protons and 4 neutrons. Lithium
Sample B has 3 protons and 3 neutrons. Lithium isotope
A is Lithium because it has 3 protons, which is the atomic number.
It is regular lithium because its atomic mass adds up to 7.
B is an isotope of lithium because with 3 protons it must be lithium, but
because its atomic mass only adds up to 6, it isn’t regular lithium,
which has 4 neutrons.
3
Li
6.94
Your Turn:
each model
Part 2: Identify
in two ways: First as what
element it is, and whether it
is a regular atom or isotope
___ protons
___ neutrons
mass = ____
Carbon
1. Sample E has 6 protons and 6 neutrons. ____________________
6
C
2.
Sample F has 6 protons and 8 neutrons. ____________________
Carbon isotope
9
12
19.
F
3. Sample G has 7 protons and 8 neutrons.
____________________
___________, ___________ 19
4.
Sample H has 7 protons and 7 neutrons.
____________________
5. Sample I has 54 protons and 77 neutrons.
____________________
6.
Sample J has 54 protons and 79 neutrons.
____________________
7. Sample K has 53 protons and 77 neutrons.
____________________
8.
Sample L has 53 protons and 74 neutrons.
____________________
9. Sample M has 27 protons and 32 neutrons.
____________________
20.
___________, ___________
10. Sample N has 27 protons and 33 neutrons.
____________________
11. Sample O has an atomic number of 90
____________________
Thorium isotope
90
and an atomic mass of 201
Th
Thorium
12. Sample P has an atomic number of 90
____________________
232.04
and an atomic mass of 232
13. Sample Q has an atomic number of 92
and an atomic mass of 238
14. Sample R has an atomic number of 92
and an atomic mass of 235
____________________
____________________
15. Sample S has an atomic number of 27
and an atomic mass of 59
16.Sample T has an atomic number of 28
and an atomic mass of 59
____________________
____________________
17. Sample U has an atomic number of 43
and an atomic mass of 98
18. Sample V has an atomic number of 43
and an atomic mass of 99
____________________
____________________
21.
___________,
___________
22.
___________,
___________
Making Models of Isotopes
Draw 3 isotopes of Helium: Helium 5, Helium 6, and Helium 7. These numbers refer to
the atomic mass. All of these isotopes have an atomic number of 2.
Using different colors or symbols, draw the protons, neutrons, and electrons of these
isotopes. Include a key to explain your drawings, and use the same key for each model.
23. Helium 5 (Atomic mass = 5)
--
+ +
--
24. Helium 6
All helium atoms
have two protons,
but helium isotopes
can have a different
number of neutrons
than shown on the
periodic table. The
protons and
neutrons add up to
the atomic mass.
2
He
4
25. Helium 7
26. Key
+
= Proton
= Neutron
--
= Electron
3
Li
6.94
27. Helium 7 has the same atomic mass as Lithium. Why isn’t it called Lithium?
______________________________________________________________________
28. Which isotope of Helium has the most density (most mass)? ____________________
29. Give a definition of isotope: ______________________________________________
______________________________________________________________________
30. How are some isotopes useful to scientists? (Hint: all of the isotopes on page 1 are
real, and may be useful in some way!) List some names and their uses: _____________
______________________________________________________________________
______________________________________________________________________
_____________________________________________________________BONUS!!!