Atomic Mass Worksheet

Atomic Mass Worksheet

Read each question carefully and answer to the best of your ability. Show all work for calculations.

1. The atomic mass unit (amu) is defined as one-twelfth the mass of a carbon-12  .

2. The number of   in an atom determines its atomic number.

3. Isotopes are atoms of the same element that have different numbers of  .

4. The average atomic mass of an element is the weighted average of the masses of its naturally occurring  .

1. Which subatomic particle contributes most significantly to the mass of an atom?

2. An element has two isotopes. Isotope 1 has a mass of 10.012 amu and an abundance of 19.9%. Isotope 2 has a mass of 11.009 amu and an abundance of 80.1%. What is the average atomic mass of this element?

1. Explain the difference between mass number and atomic mass.

2. Calculate the average atomic mass of silicon, which has three isotopes: Silicon-28 (mass = 27.977 amu, abundance = 92.23%), Silicon-29 (mass = 28.976 amu, abundance = 4.67%), and Silicon-30 (mass = 29.974 amu, abundance = 3.10%).

1. All atoms of a given element have the same atomic mass.

2. The atomic mass listed on the periodic table is the mass of the most abundant isotope.