Multiple Choice
Which of the following electron configurations for neutral atoms represents an excited state?
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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 nobelium (No)?
A
[Rn] 7s2 5f7
B
[Rn] 7s2 5f14
C
[Ne] 3s2 3p7
D
[Xe] 6s2 5d1
Verified step by step guidance1
Step 1: Identify the atomic number of nobelium (No). Nobelium has an atomic number of 102, meaning it has 102 electrons in its neutral state.
Step 2: Recall the electron configuration order, which follows the Aufbau principle. Electrons fill orbitals in the order of increasing energy levels: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, and so on.
Step 3: Recognize that nobelium is an actinide element, so its electron configuration will include filling the 5f orbitals after the 7s orbital is filled.
Step 4: Use the noble gas shorthand notation to simplify the configuration. The noble gas preceding nobelium is radon (Rn), which accounts for the first 86 electrons. The remaining electrons (102 - 86 = 16) will fill the 7s and 5f orbitals.
Step 5: Fill the 7s orbital with 2 electrons, then fill the 5f orbital with the remaining 14 electrons to complete the configuration as [Rn] 7s2 5f14.
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