To determine which element has atoms with valence electrons in a higher energy level than those of calcium (Ca), we first need to know the electron configuration and valence electron details of calcium.
Calcium (Ca) has an atomic number of 20. Its electron configuration is:
\[ \text{Ca: } 1s^2 2s^2 2p^6 3s^2 \]
The valence electrons of calcium are in the 4th energy level (the 3s electrons) because we consider the outermost shell.
Now, let's analyze the options provided:
A) Cesium (Cs): The atomic number is 55, and the electron configuration is \( [Xe] 6s^1 \). The valence electron (6s) is in the 6th energy level, which is higher than the 4th.
B) Oxygen (O): The atomic number is 8, and the electron configuration is \( 1s^2 2s^2 2p^4 \). The valence electrons (in the 2s and 2p subshells) are in the 2nd energy level, which is lower than the 4th.
C) Lithium (Li): The atomic number is 3, and the electron configuration is \( 1s^2 2s^1 \). The valence electron (2s) is in the 2nd energy level, which is lower than the 4th.
D) Bromine (Br): The atomic number is 35, and the electron configuration is \( [Ar] 4s^2 3d^{10} 4p^5 \). The valence electrons (4s and 4p) are in the 4th energy level, equal to that of calcium.
The only element from the options that has its valence electrons in a higher energy level than those of calcium is:
A) cesium (Cs).
1 answer