Electronegativity

What can very few compounds do?

Come even close to being purely ionic

What can bonds between atoms of a single element be?

Purely covalent

Where can most compounds come from?

Somewhere in between the 2 extremes, meaning they've often got ionic and covalent properties

What does a bond having more covalent or ionic character depend on?

The difference in electronegativity between the bonded atoms

What is electronegativity?

The ability of an atom to attract the bonding electrons in a covalent bond.

How is electronegativity measured?

Pauling scale

What does a higher number mean?

An element is better able to attract the bonding electrons.

What does electronegativity tend to do, ignoring the noble gases and hydrogen?

Increase across periods and decrease down groups

Which are the most electronegative?

Fluorine is the most electronegative, with oxygen, nitrogen and chlorine also very strongly electronegative