Question

The electronic configuration of chromium violates [ ]

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Answer 1

Explanation:

Some elements do not follow the Afbau principle, there are some alternate ways that electrons can arrange themselves that give these elements better stability.

Explanation:

Using the Afbau principle, you would write the following electron configurations

Cr = [Ar] 4s2 3d4

Cu = [Ar] 4s2 3d9

The actual electron configurations are:

Cr = [Ar] 4s1 3d5

Cu = [Ar] 4s1 3d10

To understand why this occurs, it is important to realize that...

1. Completely filled sublevels are more stable than partially filled sublevels.

2. A sublevel which is exactly half filled is more stable than a partially filled sublevel which is not half full.

3. Electrons are lazy and will do whatever places them in the lowest energy state = which is the most stable state

In both examples, an electron moves from the 4s sublevel to produce a 1/2 full 3d (Cr) or completely filled 3d (Cu). This gives the atom greater stability so the change is favorable.

Answer 2

The electronic configuration of chromium violates the Aufbau principle.

- The atomic no of chromium is 24.

- According to the Aufbau principle, the electronic configuration of an element with atomic no 24 should be given as:

1s², 2s² 2p⁶, 3s² 3p⁶, 4s², 3d⁴.

- But the actual electronic configuration of Cr is 1s², 2s² 2p⁶, 3s² 3p⁶, 4s¹, 3d⁵.

- This is due to the extra stability of d⁵ electronic configuration.

- Hence, the electronic configuration of chromium violates the Aufbau principle.