Final answer:
Oxygen, having 6 electrons in its outermost shell, needs 2 more to complete its shell to achieve a stable state. Therefore, oxygen is more likely to gain 2 electrons. Because of this, oxygen is considered highly electronegative.
Step-by-step explanation:
Oxygen has 6 electrons in its outermost shell, which leaves 2 vacancy spots. The goal of most atoms, including oxygen, is to have a full outer shell - typically 8 electrons in total – as this is a stable configuration. This principle, known as the octet rule, motivates atoms to interact with others through gaining, losing, or sharing electrons. In oxygen's case, it is easier to gain 2 electrons to fill its outer shell rather than losing its existing 6 electrons.
Therefore, an uncharged atom of oxygen is more likely to gain 2 electrons. The tendency of an atom to attract electrons towards itself is defined as electronegativity. Since oxygen tends to attract electrons to fill its outer shell, it is, therefore, highly electronegative.
The stability achieved by reaching an octet state leads to chemical bonding. In oxygen's case, for example, two oxygen atoms can share electrons with each other, forming a double covalent bond (O=O), and thereby reaching their desired octet state.
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