Question

Which element has atoms with valence electrons in a higher energy level than those of calcium?
A. cesium
B. Lithium
C. bromine
D. oxygen

Answer 1

To determine which element has atoms with valence electrons in a higher energy level than those of calcium, we need to look at the electron configuration and energy levels of valence electrons for each element:

- Calcium (Ca) has the atomic number 20 with the electron configuration: \( [Ar] 4s^2 \). The valence electrons (2) are in the 4th energy level.

Now, let's analyze the options:

A. **Cesium (Cs)**: Atomic number 55, electron configuration: \( [Xe] 6s^1 \). The valence electron is in the 6th energy level.

B. **Lithium (Li)**: Atomic number 3, electron configuration: \( 1s^2 2s^1 \). The valence electron is in the 2nd energy level.

C. **Bromine (Br)**: Atomic number 35, electron configuration: \( [Ar] 4s^2 3d^{10} 4p^5 \). The valence electrons are in the 4th energy level.

D. **Oxygen (O)**: Atomic number 8, electron configuration: \( 1s^2 2s^2 2p^4 \). The valence electrons are in the 2nd energy level.

From this analysis, only **cesium (A)** has valence electrons in a higher energy level (6th energy level) than calcium (4th energy level).

The correct answer is **A. cesium**.