To determine which element has valence electrons in a higher energy level than those of calcium (Ca), we first need to identify the electron configuration of calcium.
Calcium (Ca) has an atomic number of 20, and its electron configuration is: \[ \text{Ca: } 1s^2 2s^2 2p^6 3s^2 \]
The valence electrons for calcium are in the 4th energy level (3s sublevel).
Now, let's analyze the options:
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Cesium (Cs): Atomic number 55
- Electron configuration: \[ \text{Cs: } [Xe] 6s^1 \]
- Valence electrons are in the 6th energy level.
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Lithium (Li): Atomic number 3
- Electron configuration: \[ \text{Li: } 1s^2 2s^1 \]
- Valence electrons are in the 2nd energy level.
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Oxygen (O): Atomic number 8
- Electron configuration: \[ \text{O: } 1s^2 2s^2 2p^4 \]
- Valence electrons are in the 2nd energy level.
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Bromine (Br): Atomic number 35
- Electron configuration: \[ \text{Br: } [Ar] 4s^2 3d^{10} 4p^5 \]
- Valence electrons are in the 4th energy level.
Among these options, only cesium (Cs) has valence electrons in a higher energy level (6th) than those of calcium (4th).
Therefore, the correct answer is: cesium (Cs).
1 answer