Periodic Properties Of The Elements Page 4

2. Ionization Energy

IE = energy required to remove an electron from an atom or ion

(always endothermic, positive values)

Li (g) → Li + (g) + e -

e.g.,

I.E. = 520 kJ/mole

IE Increases

Inc

Periodic Table

3. Electron Affinity

EA = energy released when an electron is added to an atom or ion

(usually exothermic, negative EA values)

Cl (g) + e - → Cl - (g)

e.g.,

EA = -348 kJ/mole

EA Increases

(more exothermic)

Inc

Periodic Table

The general trends in all of these properties indicate that

there is a special stability associated with filled-shell

configurations as in the inert gases.

Atoms tend to gain or lose an electron or two in order to

achieve a stable "inert gas configuration" -- many important

consequences of this in chemical bonding.

Page 4

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