An atom of element Be has four protons, four electrons, and five neutrons. Which element below could be an isotope of this atom? Sodium-10 beryllium-10 boron-9 carbon-9

beryllium-10

Explanation:

An isotope is an atom of the same element that has a different number of neutrons.

This means that an isotope of beryllium (Be) would have to be beryllium as well.

The number 10 references the fact that it has four protons and six neutrons:

4 protons + 6 neutrons = 10

While usually the element has 5 neutrons, so it is beryllium-9.

beryllium 10

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Explanation:

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.