Multiple Choice
Which element has the following ground state electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^5?
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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 a neutral selenium (Se) atom?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8 4p^6
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^2
Verified step by step guidance1
Step 1: Determine the atomic number of selenium (Se), which tells you the total number of electrons in a neutral atom. Selenium has an atomic number of 34, so it has 34 electrons.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.
Step 3: Fill the orbitals with electrons following the maximum capacity of each orbital: s orbitals hold 2 electrons, p orbitals hold 6, and d orbitals hold 10.
Step 4: Assign electrons to each orbital in order until all 34 electrons are placed. This means filling 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^{10}, and then placing the remaining electrons in the 4p orbital.
Step 5: Verify that the total number of electrons adds up to 34 and that the electron configuration matches the expected pattern for selenium, which ends with 4p^4 electrons.
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