Which orbital notation represents an atom of beryllium (Be) in the ground state?

• A. 1s^2 2p^2
• B. 1s^2 2s^1 2p^1
• C. 1s^2 2s^1
• D. 1s^2 2s^2

Answer: (D)

Verified step by step guidance

1. Identify the atomic number of beryllium (Be), which is 4. This means a neutral Be atom has 4 electrons.
2. Recall the order in which electrons fill orbitals according to the Aufbau principle: electrons fill the lowest energy orbitals first.
3. Write the electron configuration by filling orbitals in order: first fill the 1s orbital with 2 electrons, then the 2s orbital with the remaining 2 electrons.
4. Express the electron configuration using orbital notation, showing the number of electrons in each orbital: \$1s^2 2s^2$.
5. Verify that this configuration corresponds to the ground state of beryllium, where all electrons occupy the lowest possible energy levels without unpaired electrons in higher orbitals.