4.5: Average Atomic Mass

An imaginary element has three naturally-occurring isotopes.  80% of the isotopes have a mass of 3 amu, 15% have a mass of 4 amu, and 5% have a mass of 5 amu. The average atomic mass of this imaginary element will be closest to

• 3 amu

• 4 amu

• 5 amu

• 12 amu

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

Chlorine has two naturally occurring isotopes, chlorine-35 and chlorine-37, The atomic mass of chlorine is 35.45. Which of these two isotopes of chlorine is more abundant?

• chlorine-35

• chlorine-37

• Cannot be determined from the information provided.

The image shows a square from the periodic table. What does the number at the very bottom of the square tell you?

• atomic number

• average atomic mass

• mass number

• number of neutrons

Tags

NGSS.HS-PS1-1

What is the unit we use for average atomic mass?

• amu

• g

• g/mol

• g/mL

Calcium has three different isotopes. One has a mass of 35 amu; another has a mass of 41 amu; and another has a mass of 40 amu. Based on calcium's average atomic mass (from the periodic table), which isotope of calcium is probably the most abundant?

• 35 amu

• 40 amu

• 41 amu

• impossible to tell

A hypothetical element has 3 naturally-occurring isotopes, as shown in the chart. Calculate this element's average atomic mass.

• 57.2 amu

• 84.5 amu

• 60.0 amu

• 56.7 amu

Tags

NGSS.HS-PS1-7

An element has 2 naturally-occurring isotopes. One of them has a mass of 112 amu and an abundance of 60%. The other has a mass of 113 amu and an abundance of 40%. What element is it?

• copernicium

• nihonium

• cadmium

• neodymium