Atomic Structure and Average Atomic Mass

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

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What does the 1.00794 stand for?

• Hydrogen
• atomic number
• atomic mass
• atomic explosion

What is the atomic number for an element with three protons?

• 2
• 1
• 3
• 6

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

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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

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CCSS.HSS.MD.A.2

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CCSS.HSS.MD.B.5

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

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CCSS.HSS.MD.A.3

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For a given element, the atomic number indicates the number of _____

• protons in the nucleus
• neutron in the nucleus
• electrons in the atom
• nucleons in the atom

If an atom contains exactly three protons, then it's an atom of _____

• lithium
• gold
• nitrogen
• carbon

How many neutrons does the isotope of lithium have?

• 8
• 3
• 4
• 5