Calcium (Ca) has the electron configuration of [Ar] 4s², meaning its valence electrons are in the 4th energy level (n=4).
To identify which element has valence electrons in a higher energy level than calcium, we need to consider the other options:
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Bromine (Br): The electron configuration is [Ar] 4s² 3d¹⁰ 4p⁵. The valence electrons are in the 4th energy level, so this does not qualify.
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Cesium (Cs): The electron configuration is [Xe] 6s¹. The valence electron is in the 6th energy level (n=6), which is higher than calcium.
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Oxygen (O): The electron configuration is 1s² 2s² 2p⁴. The valence electrons are in the 2nd energy level (n=2), so this does not qualify.
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Lithium (Li): The electron configuration is 1s² 2s¹. The valence electron is in the 2nd energy level (n=2), so this does not qualify.
Therefore, the correct response is cesium (Cs).