Video Transcript
The following table shows the
number of protons and neutrons in different atoms. Which statement makes a valid
comparison between a pair of listed atoms? (A) Carbon and nitrogen have the
same atomic numbers. (B) Carbon has a higher atomic
number than oxygen. (C) Nitrogen and oxygen have the
same mass numbers. (D) Nitrogen has a higher mass
number than carbon. (E) Oxygen has a lower mass number
than carbon.
To answer this question, we need to
compare the three atoms in the given table. We’ve been told how many protons
and neutrons each atom has. However, none of the answer choices
involve comparing the number of protons or neutrons in each atom. But we do see the terms “atomic
number” and “mass number” in each of the answer choices. So, we’ll need to know what these
terms mean and how they relate to the number of protons and number of neutrons in
order to compare the atoms.
Let’s start by looking at the
answer choices that involve the term “atomic number.” Atomic number is the number of
protons in the nucleus of the atom. Since each of the atoms provided
have a different number of protons, they each have a different atomic number. Knowing this, we can eliminate
answer choice (A) as carbon and nitrogen do not have the same atomic numbers. We can also eliminate answer choice
(B) as carbon does not have a higher atomic number than oxygen.
Now, we can think about the answer
choices that contain the term “mass number.” Mass number is the number of
protons and neutrons in the nucleus of an atom. So, we can calculate the mass
number of each atom by adding together the number of protons and the number of
neutrons it contains. The mass number of the carbon atom
is 12, the mass number of the oxygen atom is 16, and the mass number of the nitrogen
atom is 14. Knowing this, we can eliminate
answer choice (C) because the nitrogen atom and the oxygen atom do not have the same
mass numbers. We can also eliminate answer choice
(E) as the oxygen atom does not have a lower mass number than the carbon atom.
This leaves us with answer choice
(D). The nitrogen atom does have a
higher mass number than the carbon atom. So, the statement which makes a
valid comparison between a pair of listed atoms is answer choice (D). Nitrogen has a higher mass number
than carbon.
