객관식
Which of the following atoms has six valence electrons?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
Multiple Choice
How many valence electrons does strontium (Sr) have?
A
6
B
8
C
2
D
4
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검증된 단계별 안내1
Identify the atomic number of strontium (Sr), which is 38. This tells us the total number of electrons in a neutral Sr atom.
Determine the electron configuration of Sr by filling orbitals according to the Aufbau principle: start from 1s and move up to the 5s orbital.
Write the electron configuration for Sr: \$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2$.
Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number, n). For Sr, this is the 5th shell.
Count the electrons in the 5th shell (5s orbital), which gives the number of valence electrons for Sr. In this case, it is 2.
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