Multiple Choice
Consider the following electron configurations. Which atom is expected to be the most stable?A) 1s^2 2s^2 2p^6B) 1s^2 2s^2 2p^5C) 1s^2 2s^2 2p^4D) 1s^2 2s^2 2p^3
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct electron configuration for strontium (Sr)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5p^2
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 4d^{10}
Verified step by step guidance1
Identify the atomic number of strontium (Sr), which is 38. This means Sr has 38 electrons to be placed in orbitals according to the Aufbau principle.
Recall the order of filling orbitals based on increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, and so on.
Fill the orbitals with electrons following the order and the maximum number of electrons each orbital can hold: s (2 electrons), p (6 electrons), d (10 electrons).
After filling up to 4p^6 (which accounts for 36 electrons), place the remaining 2 electrons in the next lowest energy orbital, which is 5s.
Verify that the electron configuration ends with 5s^2, confirming the correct configuration for Sr is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2$.
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