https://en.wikipedia.org/wiki/Lanthanide

https://en.wikipedia.org/wiki/Prontosil

https://en.wikipedia.org/wiki/Technetium#:~:text=Technetium%20is%20a%20chemical%20element,produced%20as%20a%20synthetic%20element.

Electron atomic and molecular orbitals

A Bohr diagram of lithium

In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s² 2s² 2p⁶, meaning that the 1s, 2s and 2p subshells are occupied by 2, 2 and 6 electrons respectively.

Electronic configurations describe each electron as moving independently in an orbital, in an average field created by all other orbitals. Mathematically, configurations are described by Slater determinants or configuration state functions.

According to the laws of quantum mechanics, for systems with only one electron, a level of energy is associated with each electron configuration and in certain conditions, electrons are able to move from one configuration to another by the emission or absorption of a quantum of energy, in the form of a photon.

Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements. This is also useful for describing the chemical bonds that hold atoms together. In bulk materials, this same idea helps explain the peculiar properties of lasers and semiconductors.

Shells and subshells

Main article: Electron shells (l = 0)p (l = 1)m = 0m = 0m = ±1sp_zp_xp_yn = 1n = 2

Electron configuration was first conceived under the Bohr model of the atom, and it is still common to speak of shells and subshells despite the advances in understanding of the quantum-mechanical nature of electrons.

An electron shell is the set of allowed states that share the same principal quantum number, n (the number before the letter in the orbital label), that electrons may occupy. An atom’s nth electron shell can accommodate 2n² electrons. For example, the first shell can accommodate 2 electrons, the second shell 8 electrons, the third shell 18 electrons and so on. The factor of two arises because the allowed states are doubled due to electron spin—each atomic orbital admits up to two otherwise identical electrons with opposite spin, one with a spin +1⁄2 (usually denoted by an up-arrow) and one with a spin of −1⁄2 (with a down-arrow).

A subshell is the set of states defined by a common azimuthal quantum number, l, within a shell. The value of l is in the range from 0 to n − 1. The values l = 0, 1, 2, 3 correspond to the s, p, d, and f labels, respectively. For example, the 3d subshell has n = 3 and l = 2. The maximum number of electrons that can be placed in a subshell is given by 2(2l + 1). This gives two electrons in an s subshell, six electrons in a p subshell, ten electrons in a d subshell and fourteen electrons in an f subshell.

The numbers of electrons that can occupy each shell and each subshell arise from the equations of quantum mechanics, in particular the Pauli exclusion principle, which states that no two electrons in the same atom can have the same values of the four quantum numbers.

https://en.wikipedia.org/wiki/Electron_configuration

Dubnium is a synthetic chemical element with the symbol Db and atomic number 105. It is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of about 16 hours. This greatly limits extended research on the element.

Dubnium does not occur naturally on Earth and is produced artificially. The Soviet Joint Institute for Nuclear Research (JINR) claimed the first discovery of the element in 1968, followed by the American Lawrence Berkeley Laboratory in 1970. Both teams proposed their names for the new element and used them without formal approval. The long-standing dispute was resolved in 1993 by an official investigation of the discovery claims by the Transfermium Working Group, formed by the International Union of Pure and Applied Chemistry and the International Union of Pure and Applied Physics, resulting in credit for the discovery being officially shared between both teams. The element was formally named dubnium in 1997 after the town of Dubna, the site of the JINR.

Theoretical research establishes dubnium as a member of group 5 in the 6d series of transition metals, placing it under vanadium, niobium, and tantalum. Dubnium should share most properties, such as its valence electron configuration and having a dominant +5 oxidation state, with the other group 5 elements, with a few anomalies due to relativistic effects. A limited investigation of dubnium chemistry has confirmed this.

https://en.wikipedia.org/wiki/Dubnium