Based on quantum mechanical theory, the electronic configuration of
Pd(Z = 46) is
(a) 4d⁹5s¹
(b) 4d¹⁰
(c) 4d8 5s¹
(d) 4d 10 5s²
Answer with explaination
Answers
Answer:
This is actually a rather complicated topic, but the answer is essentially that the notion of electronic configuration for Pd and Pt is not even a well-defined concept to begin with and may actually have little or no correspondence with physical reality. Here is a summary of why it is complicated:
1. The notion of electronic configuration begins to break down for the higher elements because for an electronic configuration to exist, the electrons are assumed to populate orbitals that resemble the orbitals of the hydrogen atom. This is where the nomenclature 1s, 2p, 3d, ... actually comes from. In atoms with many electrons, this picture breaks down because the orbitals in these atoms actually don't resemble hydrogenic orbitals. The principal causes for this breakdown are
a) relativistic effects (the expected velocity of electrons in these orbitals approach a significant fraction of the speed of light)
b) electron correlation (the presence of electrons in other orbitals significantly affect the properties of electrons in other orbitals)
2. The effect of electron correlation is more severe than just distorting orbitals, it also means that the very notion of electron configuration is insufficient to describe the physical and chemical properties of the atom. This is what makes condensed matter physics so complicated and why it is a great challenge to derive chemistry from quantum mechanics, despite the assertions of physicists like Paul Dirac. It is sometimes convenient to distinguish between two types of electron correlation:
a) Nondynamical correlation: there are atoms for which a single electronic configuration is not sufficient to describe the ground state, i.e. they exhibit what is known as multireference character.
b) Dynamical correlation: the very presence of electrons in certain orbitals can profoundly change the shape (and hence physical properties) of electrons in other orbitals. The very fact that electrons are all negatively charged and that like charges repel is mostly ignored in one-electron theories like Hartree-Fock theory.
3. There is also the question of what is called population analysis: given that all electrons are indistinguishable, how can you figure out which ones are in a, say, 3d orbital, given its wavefunction? It turns out that there is no unique way to calculate this, and that oftentimes you can get very different answers depending on how you do this calculation. For example, three very common methods are Mulliken population analysis, Lowdin population analysis, and natural population analysis. They all differ in how they treat coherence (entanglement) between electrons in different orbitals, which can result in different populations.
Summary: the notion of electronic configuration belies several often unappreciated approximations for the actual electronic structure of an atom or molecules. These approximations break down for heavy atoms, making the very notion of electronic configuration difficult to pin down precisely. Nevertheless, this is almost certainly not the answer one expects at the level of AP Chemistry