Question

atomic numbers and electron configurations
quiz complete
1 2 3 4 5 6 7 8 9 10
which is the electron configuration for lithium?
○ 1s²
○ 2s³
○ 1s²2s¹
○ 1s¹2s²

Explanation:

Step1: Find lithium's atomic number

Lithium has an atomic number of 3, so it has 3 electrons.

Step2: Fill orbitals by Aufbau principle

First fill 1s orbital (max 2 electrons): $1s^2$. Remaining 1 electron fills 2s orbital: $2s^1$.

Step3: Combine orbitals

Combine to get full configuration: $1s^22s^1$

Answer:

1s²2s¹