The atomic number of scandium is 21. What is its ground state electronic configuration?
Correct answer: B. 1s22s22p63s23p63d14s2
- A. 1s22s22p63s23p63d3
- B. 1s22s22p63s23p63d14s2
- C. 1s22s22p63s23p63d34s2
- D. 1s22s22p63s23p63d34p1
Explanation
The electronic configuration of an atom is determined by the Aufbau Principle, which states that electrons fill the lowest energy orbitals first. For scandium, with an atomic number of 21, the correct ground state configuration is 1s22s22p63s23p63d14s2. This configuration fills the 4s orbital before starting to fill the 3d orbital, in accordance with the energy order of orbitals. The other options incorrectly fill the orbitals or suggest an incorrect order of electron filling, which does not represent the lowest energy, most stable configuration.
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About Electronic Configuration
Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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