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The Orbital Exponent Efficacy to Study the Periodic Parameters
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
We know that the effective ‘nucleus-electron’ attraction is proportional to the effective nuclear charge (Zeff) and inversely proportional to the effective principal quantum number (n*). The effective nuclear charge increases gradually while we are going across a period where the effective quantum number remains constant. Thus, along a period, the effective ‘nucleus-electron’ attraction depends mainly on the effective nuclear charge as other factors (n*) remains constant. But in the next period, they both jump in number. The second factor, the effective principal quantum number, is the dominating one while we are going across a group. Thus, the consideration of only effective nuclear charge to explain the periodicity of periods and groups is erroneous. Alternatively, the effective attraction power of the nucleus upon the electron can be described by the orbital exponent (ξ) – the ratio of the effective nuclear charge and the effective principal quantum numbers, i.e., Zeff: n*. The orbital exponent, ξ, is simply defined as: ξ=Zeff/n*
2018 Table of static dipole polarizabilities of the neutral elements in the periodic table*
Published in Molecular Physics, 2019
Peter Schwerdtfeger, Jeffrey K. Nagle
Some general periodic trends are apparent from a consideration of the polarizabilities listed in Figure 1. In very nearly all cases, polarizabilities decrease with increase in atomic number for each nl group of elements (e.g., the 2p elements B-Ne). This reflects the well-known decrease in size with increasing atomic number for elements in a given row of the periodic table, an effect generally attributed to increasing effective nuclear charge. Polarizabilities have units of volume, and the proportionality between atomic polarizability and volume is well known [234,235]. In fact, polarizabilities provide a nearly unique direct measure of the size of an isolated atom [236].
A scale of absolute hardness based on the conjoint action of other properties
Published in Molecular Physics, 2022
Swetha Sara Sabu, S. Jane Anto Simplica, Hiteshi Tandon, Tanmoy Chakraborty
Polarizability is understood as the distortion in electron cloud due to applied electric field. When outermost electrons are held less strongly, they can be easily distorted. When the radius of an atom is small, effective nuclear charge holds outermost electrons tightly, making it less polarizable. Decrease in polarizability may tend to increase hardness. Szarek and Grochala [20] related atomic radius to polarizability (α) and hardness (η) as: