& Periodic Properties By: Nicole and Savannah
atomic radius may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.
A+ represents an ion of element. A with a single positive charge, referred to as a 1+ ion.
An ion is an atom or group of bonded atoms that has a positive or negative charge. Any process that results in the formation of an ion is referred to as ionization.
The energy required to remove one electron from a neutral atom of an element is the ionization energy, IE (or first ionization energy, IE1)
In general, first ionization energies increase across a period and decrease down a group.
Group 1 elements have the lowest first ionization energies in their respective periods. Therefore, they lose electrons most easily. This increases their reactivity because the electrons are easier to loose. The low reactivity of the noble gases is partly based on this difficulty of electron removal.
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).
A + e- ----> A- + energy
A + e- + energy -----> A-
Adding Electrons to Negative Ions
A negative ion is known as a anion. The formation of an anion by the addition of one or more electrons always leads to an increase in atomic radius. This is because the total positive charge of the nucleus remains unchanged when an electron is added to an atom or an ion. So the electrons are not drawn to the nucleus as strongly as they were before te addition of the extra electron. The electron cloud also spreads out because of greater repulsion between the increased number of electrons.
The electrons available to be lost, gained, or shared in the formation of chemical compounds are referred to as valence electrons. Valence electrons are often located in incompletely filled main-energy levels.