Final answer:
Selenium in period four gains two electrons to achieve an octet in its outermost shell.
Explanation:
In this case, the element with six valence electrons in period four is Selenium. Selenium will gain two electrons to obtain an octet in its outermost electron shell, resulting in an ion with a 2- charge (Se2-).
Learn more about Valence electrons in Selenium here:
https://brainly.com/question/2027552
