And Periodic Properties
atomic radius- one-half the distances between nuclei of identical atoms that are bonded together.
The trends to smaller atoms across a period is caused by the increasing positive charge of the nucleus.
In general, the atomic radii of the main-group elements increase down a group
A+ + e- (A+ = ion with a single positive charge)
ionization- any process that results in the formation of an ion
Ionization energy (IE)- the energy required to remove one electron from a neutral atom of an element
Ionization energies of the main-group elements increase across each period
Among the main-group elements, ionization energy generally decrease down the groups
Removing Electrons from Positive Ions
- Each successive electron removed from an ion feels an increasingly stronger effective nuclear charge (the nuclear charge minus the electron shielding)
Electron affinity - energy change that occurs when an electron is acquired by a neutral atom
A + e- ⇒ A- +energy
A + e- + energy ⇒ A-
As electrons add to the same p sublevel of atoms with increasing nuclear charge, electron
exception - between Groups 14&15
electrons add with greater difficulty down a group
Adding Electrons to Negative Ions
- second electron affinities are all positive
Electronegativity - measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound
Electronegativities tend to increase across each period, although there are exceptions
- Electronegativities tend to either decrease down a group or remain about the same
Periodic Properties of the d- and f-block elements
As the number of electrons in the d sublevel increase, the radii increase because of repulsion among the electrons
Ionization energies of the d-block and f-block elements generally increase across the periods
Ion Formation and Ionic Radii
Electrons in the highest occupied sublevel are always removed first
- The general trend for electronegativity values to increase as radii decrease
Brandi Hageman & Kaitlyn Imoehl
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