Chapter 4 Extra Practice
1.
How many protons and electrons are in the following atoms?
a.
Gallium: _______31, 31___________________________
b. Silicon: __________14,14__________________________
c. Calcium: ________20,20___________________________
2. What is the atomic number and element name for each of the following?
a.
An atom with 37 electrons: 37, Rubidium Rb
b. An atom with 72 protons: 72, Hafnium ,Hf
3. An isotope of copper contains 29 electrons, 29 protons and 36 neutrons.
a. What the atomic number? 29
b.
What is the mass number for this isotope? 65
4. An isotope of uranium contains 92 electrons and 144 neutrons. What is the mass number for
this isotope? 92 + 144 = 236
5. Complete the chart below for the following isotopes:
isotope
protons
electrons
neutrons
Yttrium -88
39
39
49
Arsenic – 75
33
33
42
Xenon – 129
54
54
75
Bromine – 79
35
35
44
Gold – 197
79
79
118
Helium - 4
2
2
2
6. An element has two naturally occurring istopes: 14X and 15X. 14X has a mass of 14.00307 amu
and a relative abundance of 99.63%. 15X has a mass of 15.00011 amu and a relative abundance
of 0.37%. Identify the unknown element.
14
X mass contribution: (14.00307)(.9963) = 13.95126 amu
15
X mass contribution: (15.00011)(.0037) = 0.05550 amu
Atomic mass: 13.95126 amu + 0.05550 amu = 14.00676 amu = nitrogen
7. Silver has two naturally occurring isotopes: Ag-107 has an abundance of 51.82% and a mass of
106.9 amu. Ag-109 has a relative abundance of 48.18% and a mass of 108.9 amu. Calculate the
atomic mass of silver.
Ag-107 = (106.9 amu)(0.5182) = 55.3956
Ag – 109 = (108.9 amu)(0.4818) = 52.4680
55.3956 + 52.4680 = 107.8636
8. What is an atomic mass unit?
1/12 of a carbon – 12 atom
9. If Radium - 226 were to give off an alpha particle, what would its new mass and atomic numbers
be? What element would it become?
Ra226
88
α
Rn222
86