Page 74 - Chemistry eBook

First Ionization Energy
FIRST IONIZATION ENERGY: The minimum amount of energy needed to remove the most loosely bound electron
( Reffy, pp. 10-11) Reffy lists the first ionization energy of each element.
Hydrogen needs 1312 kJ/mol to remove the most loosely bonded electron.
• When an element has more valence electrons, you need more energy to pull it off.
• As you move across the period, the elements have more valence electrons, and ionization energy increases. (It gets harder to pull away electrons.)
• As you move down the group, there are more shells, so the electrons are
looser, and the ionization energy decreases. (It is easier to pull away electrons.)
Group 18 needs the highest ionization enery to remove the most loosely bound electron.
First Ionization Energy is the amount of energy needed to remove the most loosely bound electron.
74 © UNIT 3: PERIODIC TABLE OF ELEMENTS