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Hi there.
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In this question, we are looking for three different atoms or cations that have 27 electrons.
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So let's review for a moment.
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An atom is, of course, neutral.
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So that means the number of protons equals the number of electrons in a neutral atom.
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A cation, however, that is a positive ion.
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And positive ions are formed by a loss of one or more electrons.
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So cations will have fewer electrons than the neutral atom of an element.
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Okay, so we are looking for 27 electrons.
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Well, let's start out with the atom.
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And remember we said that in an atom it's neutral, so the number of electrons equals the number of protons.
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So we're looking for the element that has 27 protons.
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And that would be cobalt, because the atomic number is the number of protons.
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So cobalt with an atomic number of 27 has 27 protons, and therefore, since it's a neutral atom, it has 27 electrons.
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Okay, next, that is going to be the only atom that has 27 electrons.
01:32
Our other two choices have to be cationts or positive ions, which means they've lost one or more electrons...