Platinum Atomic Structure Explained

The question asks for the correct electronic configuration of the element Platinum (Pt). Platinum is a transition metal located in the periodic table with atomic number 78. Understanding its electronic configuration involves knowing how electrons fill the atomic orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle, while also considering common exceptions for stability.

Understanding Electron Configuration

The electronic configuration describes the arrangement of electrons within an atom's electron shells and subshells. For Platinum (Pt), with atomic number 78, we need to account for all 78 electrons.

• The noble gas preceding Platinum is Xenon (Xe), which has an atomic number of 54. Its electronic configuration is $[Xe]$.
• This means we need to determine the arrangement of the remaining 78 - 54 = 24 electrons in the shells beyond Xenon.
• The orbitals typically filled after Xenon are the 6s, 4f, and 5d subshells.
• Based on the standard filling order (Aufbau principle), we would expect electrons to fill the 6s subshell first (2 electrons), then the 4f subshell (14 electrons), and finally the 5d subshell.

Investigating Platinum's Configuration Exception

While the standard filling order suggests an electronic configuration like $[Xe] 4f^{14} 5d^8 6s^2$ (which accounts for 54 + 14 + 8 + 2 = 78 electrons), many transition metals exhibit exceptions to achieve greater stability. A more stable configuration is often achieved when subshells are either completely filled or exactly half-filled.

Platinum is one such element where an exception occurs. Instead of filling the 5d subshell with 8 electrons and leaving the 6s subshell with 2 electrons, Platinum achieves a more stable arrangement by having the 5d subshell nearly filled (9 electrons) and the 6s subshell half-filled (1 electron).

Therefore, the actual electronic configuration of Platinum (Pt) is $[Xe] 4f^{14} 5d^9 6s^1$. This configuration has a total of 54 + 14 + 9 + 1 = 78 electrons.

Analyzing the Provided Options

Let's examine each option based on our understanding:

• Option 1: $[Xe] 4f^{14} 5d^{10} 6s^0$
  This configuration has 54 + 14 + 10 + 0 = 78 electrons. While it has the correct number of electrons, it represents a fully filled 5d subshell and an empty 6s subshell. This configuration is incorrect for Platinum. It's closer to Mercury (Hg), which is $[Xe] 4f^{14} 5d^{10} 6s^2$.
• Option 2: $[Xe] 4f^{14} 5d^9 6s^1$
  This configuration has 54 + 14 + 9 + 1 = 78 electrons. This matches the known exceptional electronic configuration for Platinum (Pt), achieving greater stability with a nearly full 5d subshell and a half-filled 6s subshell. This is the correct configuration.
• Option 3: $[Xe] 4f^{14} 5d^8 6s^2$
  This configuration also has 54 + 14 + 8 + 2 = 78 electrons. However, this represents the *expected* configuration based on the standard Aufbau filling order, not the actual, more stable configuration adopted by Platinum due to exceptions in transition metal electron arrangements.
• Option 4: $[Xe] 4f^{13} 5d^{10} 6s^1$
  This configuration has 54 + 13 + 10 + 1 = 78 electrons. It incorrectly shows the 4f subshell as not fully filled ($4f^{13}$) while the 5d subshell is fully filled. This is not the correct electronic configuration for Platinum.
• Option 5: (Empty)
  This option is invalid as it contains no configuration data.

Based on the analysis, the correct electronic configuration for Platinum (Pt) is $[Xe] 4f^{14} 5d^9 6s^1$.