Ground-state electron configuration for an atom of selenium
The Correct Answer and Explanation is:
The ground-state electron configuration for an atom of selenium (Se) can be written as:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
Here’s how this configuration is determined:
- Atomic Number of Selenium: Selenium (Se) has an atomic number of 34, which means it has 34 electrons in its neutral atom.
- Filling Order: Electrons are arranged in atomic orbitals in order of increasing energy, following the Aufbau principle, the Pauli exclusion principle, and Hund’s rule.
- 1s²: The first energy level (n=1) contains only the 1s orbital, which can hold a maximum of 2 electrons.
- 2s² 2p⁶: The second energy level (n=2) contains 2s and 2p orbitals. The 2s orbital holds 2 electrons, and the 2p orbital holds 6 electrons, filling it completely.
- 3s² 3p⁶: The third energy level (n=3) contains 3s and 3p orbitals. The 3s orbital holds 2 electrons, and the 3p orbital holds 6 electrons, filling it as well.
- 4s² 3d¹⁰ 4p⁴: The fourth energy level (n=4) starts with the 4s orbital, which holds 2 electrons. After that, electrons fill the 3d orbital (which is lower in energy than the 4p), so it holds 10 electrons. Finally, the 4p orbital holds the remaining 4 electrons.
- Electron Distribution: The electron configuration shows how electrons are distributed across different orbitals of an atom, and it reflects the stability of the atom. Selenium, being a group 16 element, has 4 electrons in its outermost p-orbital (4p⁴), contributing to its chemical properties.
This arrangement is stable in the ground state because it follows the lowest energy configuration for the electrons.
