Final answer:
Boron (atomic number 5) has five electrons in its atomic structure, three of which are valence electrons. It does not gain any electrons when it becomes an anion, but rather, it loses one electron to attain a stable configuration similar to the noble gases.
Step-by-step explanation:
The student asked, "How many valence electrons does boron gain when it becomes an anion?". This question involves understanding atomic structure and ionic bonding in chemistry. An atom of boron (atomic number 5) in its neutral state has five electrons with the electron configuration 1s²2s²2p¹, meaning it has three valence electrons. However, to obtain a complete outer shell and reach stability similar to the noble gases in the periodic table, boron should gain electrons. Since the nearest noble gas is helium with two electrons, boron only needs to lose one electron to achieve a stable electron configuration, not gain. Thus, boron does not gain any electrons when it forms an anion (0).
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