To determine which element has atoms with valence electrons in a higher energy level than those of calcium (Ca), we need to consider the period in which each element is located in the periodic table. Elements in higher periods have their valence electrons in higher energy levels.
Calcium (Ca) is located in the 4th period of the periodic table.
Now let's identify the periods for the given elements:
1. Bromine (Br) is located in the 4th period.
2. Lithium (Li) is located in the 2nd period.
3. Cesium (Cs) is located in the 6th period.
4. Oxygen (O) is located in the 2nd period.
To compare their energy levels:
- Bromine is in the same 4th period as calcium, so its valence electrons are in the same energy level.
- Lithium and oxygen are in the 2nd period, which is lower than the 4th period of calcium.
- Cesium is in the 6th period, which is higher than the 4th period of calcium.
Therefore, the element from the given list that has valence electrons in a higher energy level than calcium is cesium (Cs).
