In the space below, write the full (unabbreviated) electron configurations of the following elements:
1 sodium
2 iron
3 bromine
4 barium
5 neptunium
The Correct Answer and Explanation is:
Sure! Here’s the full (unabbreviated) electron configurations for the given elements along with a detailed explanation:
1. Sodium (Na)
Atomic number = 11
Electron configuration:
1s² 2s² 2p⁶ 3s¹
2. Iron (Fe)
Atomic number = 26
Electron configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
3. Bromine (Br)
Atomic number = 35
Electron configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
4. Barium (Ba)
Atomic number = 56
Electron configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
5. Neptunium (Np)
Atomic number = 93
Electron configuration:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁴ 6d¹
Explanation (300+ words):
Electron configurations describe the distribution of electrons in an atom’s orbitals, following the Aufbau principle, Hund’s rule, and the Pauli exclusion principle. These principles determine the order in which electrons fill atomic orbitals to minimize energy.
- Aufbau principle says electrons occupy the lowest energy orbitals first.
- Hund’s rule states that electrons fill degenerate orbitals singly before pairing.
- Pauli exclusion principle dictates that no two electrons can have the same set of quantum numbers.
Sodium (Na, Z=11):
Sodium is a relatively light element. Its first 10 electrons fill the 1s, 2s, and 2p orbitals fully (these orbitals correspond to the first and second energy levels). The 11th electron occupies the next available orbital, 3s, making its outer configuration 3s¹.
Iron (Fe, Z=26):
Iron is a transition metal. After filling up to 3p⁶ (18 electrons), the next electrons fill the 4s orbital (2 electrons) and then the 3d orbitals. The 3d subshell can hold up to 10 electrons, but iron has 6 electrons here, giving 4s² 3d⁶ configuration.
Bromine (Br, Z=35):
Bromine is a halogen in period 4. After filling the 3p⁶ orbitals (18 electrons), the next electrons fill the 4s orbital (2 electrons), then fill the 3d subshell fully (10 electrons), and finally the 4p subshell with 5 electrons (halogens have 7 valence electrons total, so the 4p subshell has 5 electrons).
Barium (Ba, Z=56):
Barium is an alkaline earth metal in period 6. Its configuration includes filled 4d and 5p orbitals before filling the 6s subshell. It has two electrons in the outermost 6s orbital.
Neptunium (Np, Z=93):
Neptunium is an actinide with a complicated electron configuration. After filling the lower energy orbitals including 6p⁶, it fills 7s², then begins filling the 5f and 6d orbitals. Np has 4 electrons in 5f and 1 electron in 6d, reflecting the beginning of the actinide series, where electrons populate f orbitals.
The full configurations, as opposed to abbreviated ones (like [Ne] or [Kr]), show all orbitals from 1s upward, which helps visualize the complete distribution and energy order. This is particularly useful in understanding chemical behavior, bonding, and periodic trends in the elements
.