객관식
Which electron configuration represents an atom in an excited state (i.e., an electron has been promoted to a higher-energy orbital while a lower-energy orbital is not filled as expected in the ground state)?
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9. Electrons in Atoms and the Periodic Table
The Electron Configuration (Simplified)
Multiple Choice
Which electron configuration correctly represents a neutral lithium atom (atomic number 3) in the ground state?
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검증된 단계별 안내1
Step 1: Identify the atomic number of lithium, which is 3. This means a neutral lithium atom has 3 electrons.
Step 2: Recall the order in which electrons fill atomic orbitals, following the Aufbau principle: electrons fill the lowest energy orbitals first. The order starts with 1s, then 2s, then 2p, and so on.
Step 3: Fill the 1s orbital first, which can hold up to 2 electrons. Since lithium has 3 electrons, the first 2 will fill the 1s orbital completely.
Step 4: Place the remaining 1 electron in the next available lowest energy orbital, which is the 2s orbital.
Step 5: Write the electron configuration by showing the number of electrons in each orbital: \(1\text{s}^2\ 2\text{s}^1\). This represents the ground state electron configuration of a neutral lithium atom.
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