Isotopes and 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.

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

Do the following atoms belong to the same element? Explain
       Aluminum-27
       An atom with 14 protons and 13 neutrons

• Yes because they have the same number of protons
• Yes because they have the same mass
• No because they have different number of protons
• No because they have different number of neutrons

What is the atomic number of Neon, Ne?

• 10
• 20.1798
• 10.1798
• 7

A neutral atom of the isotope ²⁶₁₂Mg would consist of

• 12 protons, 26 neutrons, 26 electrons
• 26 protons, 12 neutrons, 26 electrons
• 26 protons, 14 neutrons, 14 electrons
• 12 protons, 14 neutrons, 12 electrons

A neutral atom would become an ion that has a charge of 2+ by 

• Losing two protons
• Losing two neutrons
• Losing two electrons

On the periodic table, how is atomic mass represented?

• As an average of the mass of different isotopes
• as the exact mass of every atom
• as the mass of the most common isotopes
• As the masses of all protons added together

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