Average Atomic Mass Calculations

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.
How many protons does this element have?

• 32

• 33

• 34

• no way to know

An element has three different isotopes. One has a mass of 35.00 amu; another has a mass of 36.00  amu; and another has a mass of 38.00  amu. What is the average atomic mass of this element?

• 36.33 amu

• 37.00 amu

• 12.11 amu

• impossible to tell

Tags

NGSS.MS-PS1-2

An isotope has three forms.  30% have a mass of 4 amu, 20% have a mass of 5 amu and 50% have a mass of 3 amu.  Average atomic mass will be closest to

• 2 amu

• 3 amu

• 4 amu

• 5 amu

Calcium has three different isotopes. One has a mass of 35.00 amu; another has a mass of 41.00 amu; and another has a mass of 40.00 amu. Which isotope is the most abundant of the three?

• 40.00 amu

• 41.00 amu

• 35.00 amu

• impossible to tell

Which of the following statements is true according to modern atomic theory?

• Atoms of the same element may have different masses.

• Atoms may be divided in ordinary chemical reactions.

• Atoms can never combine with any other atoms.

• Cathode rays are composed of protons..

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The average atomic mass of an element is the average of the atomic masses of its

• naturally occurring isotopes.

• two most abundant isotopes.

• radioactive isotopes.

• artificial isotopes.

The atomic mass of an element listed in the periodic table is the

• average atomic mass.

• relative atomic mass of the most abundant isotope.

• relative atomic mass of the most abundant radioactive isotope.

• mass number of the least abundant isotope.

Isotopes are atoms of the same element that have different

• principal chemical properties.

• masses.

• numbers of protons.

• numbers of electrons.

What is an amu

• atomic mass unit

• all matter unit

• all must unite

• atomic measurement universal

An element has two isotopes. One isotope has a mass of 10 amu and makes up 75% of the element. The other isotope has a mass of 11 amu. What is the average atomic mass of the element?

• 10.25 amu

• 10.50 amu

• 10.75 amu

• 11.00 amu