The Periodic Table Predates Quantum Mechanics

We showed in Section 2.2 how the structure of the periodic table arises from a quantum-mechanical description of the electronic structure of elements in terms of atomic orbitals. However, the origin of the periodic table predates the development of quantum 

As will be discussed in Section 2.5, the addition of two electrons to an isolated O atom to form Cr is energetically unfavorable. The anion is unstable by itself, but becomes stable if surrounded by positive ions in an ionic compound. Thus, in the formation of anions, the noble gas configuration is due more to favorable interactions with other ions than to any inherent stability of the noble gas configuration. 

Chapter 2 Many-Electron Atoms and the Periodic Tabie 

Gallium melts in a person s hand (body temperature is about 37°C). 

Using data from scattering experiments (see Section 0.2), Rutherford estimated the number of positive charges in the nucleus of a few elements, but the significance 

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