[عاطف خليفة]

* 2- Ionization potential ( energy)

“The amount of energy required to remove the most loosely bound electron completely from an isolated gaseous atom.

- It is determined from spectral measurements

a) In Periods

The ionization energy is inversely proportional to atomic radius, it increases as the atomic number increases, because the valence electrons become more strongly bound to the nucleus and need higher energy to be separated

b) In groups

It decreases as the atomic number increases because
1- Addition of new shell and increasing the atomic radius
2- This completed shells screen the nuclear charge
- These facilitate the removal of outer electrons

N.B.

1- The ionization energy of noble gase : are very high because it is difficult to remove electron from a completely filled shell

2- The second ionization energy is greater than the first ionization energy due to increasing nuclear charge.

3- The third ionization energy is much bigger because it may need to break up completely filled shell.

Ex