Video Transcript
The table below shows the atomic
number for a range of isotopes of different elements. Which isotope contains the greatest
number of down quarks?
Quarks are subatomic particles and
fundamental constituents of matter. They make up larger subatomic
particles, such as protons and neutrons. There are six types or flavors of
quarks that each contain a fractional electric charge. The question specifically asks
about the number of down quarks in an isotope. Down quarks combine with up quarks
to make protons and neutrons. A proton is composed of one down
quark and two up quarks, while a neutron is composed of one up quark and two down
quarks.
So, to determine which of the
isotopes contains the greatest number of down quarks, we first need to know how many
protons and neutrons each isotope contains. We are provided with the atomic
number of each isotope. The atomic number represents the
number of protons in the isotope. The value written after the name of
each element is the mass number. The mass number is equal to the sum
of the number of protons and the number of neutrons in the isotope. So, to determine the number of
neutrons in each isotope, we simply need to subtract the number of protons from the
mass number.
Now that we know the number of
protons and neutrons in each isotope, we can calculate the number of down quarks
each has. As each proton contains one down
quark and each neutron contains two down quarks, we can calculate the number of down
quarks in an isotope by adding the number of protons to two times the number of
neutrons.
Following this equation, we find
that a carbon-16 isotope contains six plus two times 10, or 26, down quarks. A nitrogen-15 isotope contains
seven plus two times eight, or 23, down quarks. An oxygen-16 isotope contains eight
plus two times eight, or 24, down quarks. A fluorine-17 isotope contains nine
plus two times eight, or 25, down quarks. And a neon-17 isotope contains 10
plus two times seven, or 24, down quarks.
From this, we can see that the
isotope that contains the greatest number of down quarks is carbon-16.
