Practice Problems 1 Che151
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1
2
3
4Practice Problems 4
Chapter 2
CHE 151
Graham/07
204
1.)
How many protons and neutrons are in the nuclei of
Tl atoms?
_81
protons___
_123
neutrons_
2.)
What is the atomic number, mass number and symbol for the element that has
45 protons and 58 neutrons?
Z = 45 protons
A = 103
___Rh_____
(Atomic Number)
(Mass Number)
(symbol)
3.)
Write the complete symbol for an atom with the following characteristics
39
a.)
contains 19 electrons and 20 neutrons
_
K_________
19
15
b.)
nitrogen atom with 8 neutrons
____
N______
7
80
c.)
bromine atom with a mass number of 80
_
Br________
35
201
d.)
mercury atom that contains 281 subatomic particles
____
Hg____
80
42
e.)
contains 20 protons and has a mass number of 42
Ca_________
20
60
f.)
cobalt atom with 33 neutrons
_____
Co____
27
128
g.)
iodine atom with 181 subatomic particles
_
I_________
53
36
h.)
sulfur atom with 52 subatomic particles
______
S____
16
238
i.)
uranium atom with 146 neutrons
_
U_________
92
65
j.)
copper atom with 65 nucleons
_______
Cu__
29
Magnesium occurs in nature in three isotopic forms:
4.)
relative mass
24
Mg (78.70% abundance)
23.985 amu
26
Mg (11.17% abundance)
25.983 amu
25
Mg (10.13% abundance)
24.986 amu
Calculate the atomic mass of Magnesium from these data
24
Mg:
0.7870 x 23.985 = 18.876195 = 18.88 amu
26
Mg:
0.1117 x 25.983 = 2.9023011 =
2.902 amu
25
Mg
0.1013 x 24.986 = 2.5310818 =
2.531 amu
24.313 24.31 amu
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