Project 1. Due Monday Feb. 1
This project aims to familiarize you with www.webelements.com making use of its
information about isotopomers of elements, both the stable, naturally occurring isotopes as
well as the radioactive, or radioisotopes.
You are assigned to work with only one element according to your last name.
Last name initials:
Element
Compound
D through H
Fe
FeBr3
A through C
S
SO2
J through M
Ni
Ni(CO)4
V through Z
Sr
Sr(SO4)
P through T
Cl
ClF3
The assignment is as follows for your specific element and compound:
1) List the percentages (natural abundances) of the stable, naturally occurring isotopes,
and show how they average to the atomic mass given for that element in most periodic
tables.
2) For each representative compound of that element, give (sketch the bar graph) the
isotopic bundle/pattern for the parent peak in its mass spectrum. [Note: here you may
use the Isotope Distribution Calculator found on the scientific Instruments site:
http://www.sisweb.com/mstools/isotope.htm
3) For each radioisotope of your element, give the nuclear equation that describes the
mode of decay and the time required to reduce the radioactivity from that isotope to
12.5% of the original. Note: Here you should use Webelements. For example, under the
radioisotopes of Neptunium (see next page), the radioisotope 234-Np or 234Np (this says
there are 93 protons in the nucleus and (234 – 93 ) or 141 neutrons) decays by
electron capture (EC) to turn into 234-U, or 234U. 235-Np has two paths for decay. The
nuclear equations will look something like this:
1)
2)
234 93Np
235 93Np
+ e-
+ e-
234 92U
t1/2 = 4.4 days
235 92U
4 2He + 231 91Pa
and a second mode of decay for this isotope is 235 93Np
Number three in the following table, Np-236, has three simultaneous
decay processes!
3)
Isotope
234
Np
235
Np
236
Np
237
Np
238
Np
239
Np
236 93Np
Mass / Da
Half-life
Mode of decay
234
234.04289
4.4 d
EC to U
235.04406
1.058 y
EC to 235U; α to 231Pa
236.04657
155000 y EC to 236U; α to 232Pa; β- to 236Pu
237.0481678 (23) 2.14 x 106 y α to 233Pa; SF
238.05094
2.117 d
β- to 238Pu
239.05293
2.355 d
β- to 239Pu
Nuclear spin Nuclear magnetic moment
0
5
/2
6
5
/2
3.14
2
5
/2
Here is a primer for balancing Nuclear Equations—taken from the web (???)