Consider the positions of barium Ba , sulfur cap s , silicon Si , and calcium Ca on the periodic table. The atoms of which element require the least amount of energy to give up an electron when forming chemical bonds?

The energy needed to remove an electron generally decreases down a group and increases from left to right across a period. Barium is farthest down and toward the left among these elements, so its outer electron is held least tightly. Therefore, barium requires the least energy to give up an electron.

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