Average Atomic Mass

An element has two naturally occurring isotopes. One is 10.013 amu and is 19.9% abundant. The other is 11.01 amu and is 80.1% abundant. What is the average atomic mass? What element is it?

• 9.012, Beryllium
• 12.011, Carbon
• 6.941, Lithium
• 10.812, Boron

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu
• 42.19 amu
• 10.43 amu
• 40.04 amu

_____________ are atoms that have the same atomic numbers but differing mass numbers.

• ions

• isotopes

• elements

• compound

Isotopes are elements that have the same number of ____________ but different amounts of ______________.

• same electrons but different protons

• same neutrons but different electrons

• same protons but different electrons

• same protons but different neutrons

What does the 1.00794 stand for?

• Hydrogen
• atomic number
• atomic mass
• atomic explosion

How many neutrons does the isotope of lithium have?

• 8
• 3
• 4
• 5

A neutral atom of Carbon-13 has ________ electrons and _________ neutrons

• 13, 13
• 6, 7
• 7, 7
• 6, 6

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
What is the average mass of this element?

• 74.92 amu
• 24.97 amu
• 75.01 amu
• 74.51 amu

Naturally occurring chlorine that is put in pools is 75.53 percent 35Cl (mass = 35 amu) and 24.47 percent 37Cl (mass = 37amu). Calculate the average atomic mass.

• 35.46 amu

• 35.00 amu

• 37.00 amu

• 17.00 amu