Multiple Choice
Which of the following represents the complete ground state electron configuration for a scandium (Sc) atom?
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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 argon (atomic number 18)?
A
1s^2 2s^2 2p^6 3s^2 3p^5
B
1s^2 2s^2 2p^6 3s^2 3p^2
C
1s^2 2s^2 2p^6 3s^2 3p^4
D
1s^2 2s^2 2p^6 3s^2 3p^6
Verified step by step guidance1
Step 1: Identify the atomic number of argon, which is 18. This means argon has 18 electrons to be arranged in its electron configuration.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, and so on.
Step 3: Fill the orbitals with electrons following the maximum capacity of each: 1s can hold 2 electrons, 2s can hold 2, 2p can hold 6, 3s can hold 2, and 3p can hold 6.
Step 4: Add the electrons stepwise until all 18 electrons are placed: 1s^2 (2 electrons), 2s^2 (2 electrons), 2p^6 (6 electrons), 3s^2 (2 electrons), and 3p^6 (6 electrons).
Step 5: Write the full electron configuration as $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6}$, which corresponds to a completely filled third shell and matches the noble gas argon.
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