Transition from Scandium (Sc) Onward:

 1. Transition from Scandium (Sc) Onward:

• Beginning with scandium (Sc), a new filling pattern emerges in the periodic table.
• The 3d orbital, which is lower in energy than the 4p orbital, is filled first. This marks a shift from the previous pattern observed in elements up to argon (Ar).

2. Electron Configuration for the Next Ten Elements:

• The next ten elements, including scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn), progressively occupy the five 3d orbitals.
• It's noteworthy that both chromium (Cr) and copper (Cu) deviate from the expected electron configuration. Instead of having four and nine electrons in the 3d orbitals, respectively, they adopt configurations with five and ten electrons in the 3d orbitals.
• This deviation occurs because fully filled orbitals and half-filled orbitals are more stable and have lower energy. Chromium and copper adopt configurations with extra stability, specifically d⁵ and d¹⁰, respectively, due to this principle.

3. Stable Configurations:

• Configurations with half-filled or fully filled orbitals are particularly stable.
• Examples of such stable configurations include p³, p⁶, d⁵, d¹⁰, f⁷, f¹⁴, etc.
• These stable configurations are exceptions to the standard filling pattern.

4. Filling of 4p Orbitals:

• After the saturation of the 3d orbitals, the filling of the 4p orbitals begins at gallium (Ga) and continues until krypton (Kr).
• This pattern of filling the 5s, 4d, and 5p orbitals in the next eighteen elements (from rubidium (Rb) to xenon (Xe)) is similar to the previous filling of the 4s, 3d, and 4p orbitals.

5. Transition to 6s Orbitals:

• Following this, the filling pattern transitions to the 6s orbital.
• In caesium (Cs) and barium (Ba), the 6s orbital contains one and two electrons, respectively.

6. Lanthanides and 4f and 5d Orbitals:

• Moving further down the periodic table, from lanthanum (La) to mercury (Hg), the filling of electrons takes place in the 4f and 5d orbitals.

The filling of electrons in atoms follows a specific pattern dictated by the energy levels and subshells. However, certain elements deviate from the standard filling pattern due to the extra stability associated with half-filled or fully filled orbitals. Chromium (Cr) and copper (Cu) are examples of elements that adopt these stable configurations, leading to exceptions in their electron configurations. This pattern continues as elements progress through the periodic table, with the filling of various orbitals in a systematic manner.