Multiple Choice
Which of the following is the correct electron configuration for beryllium (Be)?
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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 copper (Cu) atom?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^{10}
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^9
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^9
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10}
Verified step by step guidance1
Step 1: Identify the atomic number of copper (Cu), which is 29. This means a neutral copper atom has 29 electrons to be placed in orbitals according to the Aufbau principle.
Step 2: Recall the general order of orbital filling based on increasing energy levels: 1s, 2s, 2p, 3s, 3p, 4s, then 3d. Electrons fill these orbitals in this sequence.
Step 3: Fill the orbitals with electrons following the order and the maximum number of electrons each orbital can hold: 1s (2), 2s (2), 2p (6), 3s (2), 3p (6), 4s (2), and 3d (10). This accounts for 28 electrons.
Step 4: Since copper has 29 electrons, place the 29th electron. Copper is an exception to the typical filling order because a completely filled 3d subshell (10 electrons) and a half-filled 4s subshell (1 electron) is more stable than a filled 4s and partially filled 3d.
Step 5: Therefore, the electron configuration for copper is written as $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^{10}$, reflecting the stability gained by this arrangement.
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