To determine which element has atoms with valence electrons in a higher energy level than those of calcium (Ca), we need to consider the electron configuration of calcium and the other elements listed.
Calcium (Ca) has an atomic number of 20 and its electron configuration is: \[ \text{1s}^2 , \text{2s}^2 , \text{2p}^6 , \text{3s}^2 \]
The valence electrons for calcium are in the 4th energy level (3s) since the outermost shell that contains valence electrons is the 3rd shell.
Let's look at the other elements:
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Bromine (Br) - Atomic number 35
- Electron configuration: \[ \text{1s}^2 , \text{2s}^2 , \text{2p}^6 , \text{3s}^2 , \text{3p}^5 \]
- Valence electrons are in the 4th energy level (3s and 3p).
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Lithium (Li) - Atomic number 3
- Electron configuration: \[ \text{1s}^2 , \text{2s}^1 \]
- Valence electrons are in the 2nd energy level.
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Oxygen (O) - Atomic number 8
- Electron configuration: \[ \text{1s}^2 , \text{2s}^2 , \text{2p}^4 \]
- Valence electrons are in the 2nd energy level.
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Cesium (Cs) - Atomic number 55
- Electron configuration: \[ \text{[Xe]} , \text{6s}^1 \]
- Valence electrons are in the 6th energy level.
Among these, cesium (Cs) has valence electrons in a higher energy level (6th energy level) than calcium (4th energy level).
Therefore, the correct response is cesium (Cs).