WorksheetsIsotopes and Average Atomic Mass
Total questions: 35
Worksheet time: 40mins
What is the average mass of this element?
The atomic mass of an element is the ___.
average of the mass number and the atomic number for the element
weighted average of the masses of the isotopes of the element
total mass of the isotopes of the element
total number of subatomic particles in the nucleus
Calculate the average atomic mass of the element iron (Fe) using the following data:
[Isotope / % abundance]
[Iron 54 / 6% ] [Iron 56 / 92% ] [ Iron 57 / 2% ]
53.7 amu
54.9 amu
5592.0 amu
55.9 amu
What are the steps for finding the Average Atomic Mass?
1) write given mass, 2) write given %, 3) % to decimal, 4) Mass x abundance decimal 5) Add
1) % to decimal, 2) write given %, 3)write given mass, 4) Mass x abundance decimal 5) Add
1) write given mass, 2) write given %, 3) % to decimal, 4) Mass divided by abundance decimal 5) Add
1) write given mass, 2) write given %, 3) % to decimal, 4) Mass x abundance decimal 5) Subtract
Magnesium exists as the three isotopes shown. What is the average atomic mass of magnesium?
20.74 amu
22.56 amu
18.39 amu
24.31
Naturally occurring chlorine that is put in pools is 75.53 percent 35Cl (mass = 34.969 amu) and 24.47 percent 37Cl (mass = 36.966 amu). Calculate the average atomic mass.
35.46 amu
35.00 amu
37.00 amu
17.00 amu
Chlorine has two naturally occurring isotopes, Cl-35 and Cl-37, The atomic mass of chlorine is 35.45. Which of these two isotopes of chlorine is more abundant?
Cl-35
Cl-37
Cannot be determined from the information provided.
What do the mass numbers on the periodic table represent?
The mass of the most abundant isotope
The mass of the least abundant isotope
The average mass of the two most abundant isotopes
The average mass of all the isotopes
What is the average atomic mass for thallium, Tl, if there are two isotopes with the following masses and abundances? Tl-203 has a mass of 203 amu with an abundance of 29.5 % Tl-205 has a mass of 205 amu with an abundance of 70.5 %
203.12 amu
204.31 amu
204.41 amu
204.0 amu
A sample of cesium is 75% Cs-133, 20% Cs-132, and 5% Cs-134. What is the average atomic mass?
132.97 amu
133.00 amu
133.16 amu
132.85 amu
Element Q is an unknown element. 20Q has abundance of 90.51%, 21Q has abundance of 0.21%, and 22Q has abundance of 9.22%.
Find the average atomic mass of Q and identify the unknown element.
F with mass = 19,894 amu
Ne with mass = 20.17 amu
Sodium with mass = 22.90 amu
Mg with mass = 24.12 amu
Helium-4 has a percent abundance of 20% and Helium-5 has a percent abundance of 80%. What is the average atomic mass?
4.4 amu
4.8 amu
5.2 amu
6 amu
Hydrogen-1 has a % abundance of 20%, Hydrogen-2 has a % abundance of 30%, and Hydrogen-3 has a % abundance of 50%. What is the average atomic mass?
2.1 amu
2.3 amu
2.5 amu
3 amu
Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208. The average atomic mass of lead is 207.2. Which isotope of lead is likely to be the most abundant?
204
206
207
208
The isotopes of an element are listed below
4.35% have a mass of 49.9461 amu,
83.79% have a mass of 51.9405 amu,
9.50% have a mass of 52.9407 amu,
2.36% have a mass of 53.9389 a.m.u.
Determine the atomic mass of the element.
51.99 amu
52.19 amu
53.45 amu
17.33 amu
Element Z has 2 natural isotopes. One isotope has a mass of 15.0 amu and a relative abundance of 30%. The other isotope has a mass of 16.0 amu and a relative abundance of 70%. Estimate the average atomic mass for this one element.
15.0 amu
16.0 amu
15.7 amu
16.9 amu
Which isotope of potassium do you think is the most abundant: K-39, K-40, or K-41? The average atomic mass of potassium is 39.10 amu.
K-39
K-40
K-41
They are all equally abundant.
12 protons and 13 neutrons
Mg-12
Mg-13
Mg-25
Mg-24.305
