What is the Electronic Configuration of Chromium?

This article explains the Electronic Configuration of Chromium and how to write the Electronic Configuration of Chromium atom (Cr).

Electronic Configuration of Chromium

Electronic Configuration of Chromium Atom (Cr) (Atomic Number 24)

The atomic number of Chromium (Cr) = 24

So, let’s start writing the electronic configuration of Chromium (Cr) based upon the Aufbau Principle. According to Aufbau Principle, “the orbitals are filled up with electrons in order of their increasing energy, i.e., orbital of lowest energy are filled up first, and those with the highest energy are filled up at the end.”

• According to Aufbau Principle, the first two electrons of Chromium (Cr) are filled in 1s orbital.
• Then, the next two electrons for Chromium occupy the 2s orbital.
• And, the next 6 electrons for Chromium occupy the 2p orbital.
• Then, the next two electrons go in the 3s.
• Further, the next 6 electrons occupy the 3p orbital.
• Now, by following the same rule of the Aufbau Principle, within the remaining 6 electrons, two electrons are placed in the 4s orbital, and 4 electrons are placed in the 3d orbital. Thus, the expected electronic configuration of Chromium (Cr) will be as follows:

The expected electronic configuration of Chromium: 1s²2s²2p⁶3s²3p⁶ 3d⁴ 4s²

However, half–filled or fully-filled orbitals are more stable due to the symmetrical distribution of electrons. Therefore, one of the 4s² electrons of the Chromium atom jumps to the 3d⁵ to achieve a half-filled 3d orbital. Thus, the correct electronic configuration of the chromium atom will be as follows:

The correct electronic configuration of Chromium: 1s²2s²2p⁶3s²3p⁶ 3d⁵ 4s¹

Final Answer

Electronic configuration of Chromium atom (24): 1s²2s²2p⁶3s²3p⁶ 3d⁵ 4s¹

This electronic configuration also can be written as [Ar] 3d⁵ 4s¹

Electronic Configuration of Cr²⁺ (Atomic Number 22)

The atomic number of the Cr²⁺ is 22.

The electronic configuration of Cr²⁺: 1s²2s²2p⁶3s²3p⁶ 3d⁴ 4s⁰

Electronic Configuration of Cr³⁺ (Atomic Number 21)

The atomic number of the Cr³⁺ is 21.

The electronic configuration of Cr³⁺: 1s²2s²2p⁶3s²3p⁶ 3d³ 4s⁰