describe how a potassium atom becomes an ion and how a fluorine atom becomes an ion. state the formula of each ion.

A potassium atom has one valence electron in its outermost (fourth) energy level, and fluorine has seven valence electrons in its outermost (second) energy level. In order to obtain eight valence electrons (an octet), the potassium atom will transfer its single valence electron to the fluorine atom. This gives potassium eight valence electrons in its third energy level, and fluorine eight valence electrons in its second energy level. This also produces a potassium cation with a

1

+

charge with the formula

K

+

, and a fluoride anion with a

1

-

with the formula

F

-

.

The oppositely charged ions form an electrostatic attraction, which is the ionic bond. The compound potassium fluoride

(

KF

)

results, and since the potassium and fluoride ions have equal but opposite charges, the compound is neutral (but not the individual ions in the compound).