Which statement explains why the noble gases are so unreactive? they have one valence electron. they have eight valence electrons. they have seven valence electrons. they have two valence electrons.

The answer to your question is: The second option.

Explanation:

Atoms are stable when they gain or lose electrons to have 8 electrons.

They have one valence electron.  Noble gases have 8 electrons, not one, If they would have 1 electron they would be extremely reactive.

They have eight valence electrons. This is the right answer, noble gases have 8 electrons that is why they are unreactive.

They have seven valence electrons.  If noble gases would have 7 electrons, they would be very reactive.

They have two valence electrons. This option is incorrect, elements that have 2 electrons are reactive like Calcium, Magnesium, etc.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.