Nuclear charge
In chemistry, the nuclear charge is the charge of an atomic nucleus :
With
- the number n of protons in the nucleus and
- the elementary charge e .
In physics, however, the usual symbol of the nondimensional nuclear charge number or order number which the respective chemical element characterized. The atomic number is also - in the elementary, non- ionized state of the substance under consideration - equal to the number of electrons .
Effective nuclear charge
In atoms with several electrons, not all electrons are attracted to the same strength by the atomic nucleus: Electrons close to the nucleus shield the positive charge from the outside so that electrons distant from the nucleus are only subject to a lower force of attraction by the atomic nucleus. This shielding is taken into account by the effective nuclear charge :
with the shielding constant S according to Slater's rules . The effective nuclear charge is therefore the effective positive nuclear charge as it is "perceived" by a certain electron in a multi-electron atom.
The effective nuclear charge therefore depends on the element and the electron configuration . Like the atomic charge, it is usually given as a dimensionless effective atomic number = . It is important for understanding the ionization of atoms.
See also
literature
- Michael Binnewies, Maik Finze, Manfred Jäckel, Peer Schmidt, Helge Willner, Geoff Rayner-Canham: General and Inorganic Chemistry . 3. Edition. Springer, Berlin, Heidelberg 2016, ISBN 978-3-662-45066-6 , Chapter 3: An overview of the periodic table , doi : 10.1007 / 978-3-662-45067-3_3 .