Which electron configuration correctly represents a neutral lithium atom (atomic number 3) in the ground state?

• A. $1^{s}22^{s}2$
• B. $1^{s}22^{p}1$
• C. $1^{s}12^{s}2$
• D. $1^{s}22^{s}1$

Answer: (D)

Verified step by step guidance

1. Step 1: Identify the atomic number of lithium, which is 3. This means a neutral lithium atom has 3 electrons.
2. 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.
3. 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.
4. Step 4: Place the remaining 1 electron in the next available lowest energy orbital, which is the 2s orbital.
5. 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.