Multiple Choice
An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many electrons must barium (Ba) lose to achieve a noble-gas electron configuration?
A
8
B
1
C
6
D
2
Verified step by step guidance1
Identify the atomic number of barium (Ba), which tells you the total number of electrons in a neutral atom. Barium has an atomic number of 56, so it has 56 electrons.
Determine the electron configuration of barium in its ground state. Barium's electron configuration is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2$.
Recognize the nearest noble gas with a stable electron configuration that barium can achieve by losing electrons. The noble gas preceding barium is xenon (Xe), which has 54 electrons.
Calculate how many electrons barium must lose to have the same electron configuration as xenon. Since barium has 56 electrons and xenon has 54, barium must lose $56 - 54 = 2$ electrons.
Conclude that barium loses the two electrons in its outermost shell (the $6s^2$ electrons) to achieve the noble gas configuration of xenon.
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