Write electron configuration for silicon atom. Using Noble Gas notation write electron configuration for calcium atom.
The correct answer and explanation is:
Electron Configuration for Silicon Atom (Si):
Silicon has an atomic number of 14, meaning it has 14 electrons. The electron configuration is written by filling orbitals in order of increasing energy:
1s² 2s² 2p⁶ 3s² 3p²
This shows:
- 2 electrons in the 1s orbital
- 2 electrons in the 2s orbital
- 6 electrons in the 2p orbitals
- 2 electrons in the 3s orbital
- 2 electrons in the 3p orbitals
Noble Gas Notation for Calcium Atom (Ca):
Calcium has an atomic number of 20. Noble gas notation uses the electron configuration of the nearest noble gas preceding the element to simplify the configuration.
The noble gas before calcium is argon (Ar), which has 18 electrons. Argon’s configuration is:
[Ar] = 1s² 2s² 2p⁶ 3s² 3p⁶
Calcium has 2 electrons beyond argon’s configuration, so the full electron configuration in noble gas notation is:
[Ar] 4s²
Explanation:
Electron configurations describe the distribution of electrons in an atom’s orbitals. These configurations follow the Aufbau principle, where electrons fill the lowest energy orbitals first, then move to higher energy orbitals. The order typically goes: 1s, 2s, 2p, 3s, 3p, 4s, 3d, and so forth.
For silicon, with 14 electrons, the first 10 electrons fill the 1s, 2s, and 2p orbitals completely. The remaining 4 electrons fill the 3s and 3p orbitals. This arrangement gives silicon its chemical properties and places it in group 14 of the periodic table.
For calcium, which has 20 electrons, writing the full electron configuration is longer. Using noble gas notation, one can represent the inner, fully filled orbitals by the noble gas argon’s electron configuration. This simplifies the notation by focusing only on the valence electrons that determine chemical behavior—in calcium’s case, the two electrons in the 4s orbital.
Noble gas notation is a useful shorthand to easily identify the valence electrons and compare electron configurations among elements. Calcium, as an alkaline earth metal, has two electrons in its outermost shell, which explains its typical +2 oxidation state in compounds.