Electronegativity is the strength or ability of an atom to gain electrons.
EN and EA affinity differ in that EN is ability to gain electrons whereas EA is the desire to gain electrons. Also, EN is NOT a measured value—it is only relative.
Trend: As you proceed from:
LEFT → RIGHT EN ↑
BOTTOM → TOP EN ↑
Cl has the most EA
F has the most EN
Why? Same reasoning as electron affinity trend.
Electronegativity can be used to determine polarity.
Oxides are compounds which contain the element oxygen. Oxides can be acid, basic, or both.
The general trend is all metals combining with oxygen which lie to the LEFT of Aluminum will be BASIC (+ metals attract a OH–)
All elements to the RIGHT of Aluminum will be ACIDIC (– nonmetals attract H+)
Aluminum oxide can be BOTH ACIDIC AND BASIC, or amphoteric.