Fill in the blank. Isotopes are atoms with the same number of protons but a different number of blank.
Atoms consist of positively charged protons, neutral neutrons, and negatively charged electrons. Let’s take a look at an atom of lithium. The atom consists of three protons, four neutrons, and three electrons. In an atom, the number of positively charged protons and the number of negatively charged electrons are equal. This means that an atom will have a net neutral charge. We know from the question that an isotope of this lithium atom will have the same number of protons, but a different number of either neutrons or electrons.
So let’s see what happens if we remove one electron from the lithium atom. The new species has three protons, four neutrons, and two electrons. The number of positively charged protons and negatively charged electrons is no longer equal. This results in the species having a net positive charge. As the net charge is not neutral, this species is no longer considered an atom but rather an ion, an atom or molecule with a net electric charge.
Now let’s try changing the number of neutrons. This species has three protons, three neutrons, and three electrons. As the number of protons and the number of electrons are equal, this species has a net neutral charge. Thus, this figure also represents an atom of lithium. But we know that this atom of lithium is not exactly the same as the original, as each has a different number of neutrons. These two atoms of lithium represent isotopes: atoms with the same number of protons but a different number of neutrons.
Therefore, we should fill in the blank with the word neutrons.