Calcium (Ca) has the electron configuration of [Ar] 4s², meaning its valence electrons are in the fourth energy level (n=4).
To determine which of the listed elements has valence electrons in a higher energy level (n>4):
- Oxygen (O) has valence electrons in the second energy level (n=2).
- Cesium (Cs) has valence electrons in the sixth energy level (n=6).
- Bromine (Br) has valence electrons in the fourth energy level (n=4).
- Lithium (Li) has valence electrons in the second energy level (n=2).
Among the options, cesium (Cs) has valence electrons in a higher energy level than calcium.
The correct response is cesium (Cs).