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

What mass does a neutron have?

• 1 amu

• 0 amu

• -1 amu

• +2 amu

Oxygen has 8 protons. What is oxygen's atomic number?

• 16

• 8

• 15.999

• 0

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

• 13, 13

• 6, 7

• 7, 7

• 6, 6

Isotopes are atoms of the same element that have the same number of __________ but different number of __________ . Therefore, isotopes of the same element have different masses. 

• protons, neutrons

• protons, electrons

• neutrons, protons

• electrons, protons

What is true about a neutral atom?

• The number of protons equal the number of neutrons

• The number of protons equal the number of electrons

• The number of neutrons equal the number of electrons

• The number of protons, neutrons, and electrons are all different

Nitrogen has three occurring isotopes: Nitrogen-13, Nitrogen-14, Nitrogen-15. Which isotope is the most abundant?

• Nitrogen-13

• Nitrogen-14

• Nitrogen-15

• Based on the information given, it cannot be determined

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

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

What is atomic number?

• Number of protons in an atoms 

• Number of neutrons in an atom

• Mass of an atom

• Charge on an atom