Based on the electron configuration, how many valence electrons are in cesium, Cs?
$1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^6 5 s^2 4 d^{10} 5 p^6 6 s^1$
A. 6
B. 1
C. 55
D. 18
Answer (2)
Identify the outermost electron shell in the given electron configuration.
Count the number of electrons in the outermost shell to determine the number of valence electrons.
The outermost shell is the 6th shell ( 6 s 1 ).
Cesium has 1 valence electron.
Explanation
Understanding Valence Electrons We are asked to determine the number of valence electrons in Cesium (Cs) based on its electron configuration: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 6 6 s 1 . Valence electrons are the electrons in the outermost shell of an atom, which are involved in chemical bonding.
Identifying the Outermost Shell To find the valence electrons, we need to identify the outermost shell in the electron configuration. In this case, the electron configuration is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 6 6 s 1 . The highest number representing the electron shell is 6.
Counting Valence Electrons The outermost shell is the 6th shell, and it contains the subshell 6 s . The number of electrons in the 6 s subshell is 1, as indicated by the superscript. Therefore, Cesium (Cs) has 1 valence electron.
Final Answer Thus, Cesium (Cs) has only 1 valence electron.
Examples
Understanding valence electrons is crucial in predicting how elements will interact to form chemical bonds. For instance, knowing that Cesium has 1 valence electron helps predict that it will readily lose this electron to form a +1 ion, participating in ionic bonds with elements like chlorine, which needs one electron to complete its valence shell. This principle is fundamental in designing new materials and understanding chemical reactions.
Cesium (Cs) has 1 valence electron, which can be determined from its electron configuration as it has one electron in the outermost shell (6s). Therefore, the correct answer is option B. Valence electrons are important for understanding chemical reactivity.
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