Pretend that you are the size of an atom, observing a reaction between a potassium atom and a fluorine atom. write an account of the formation of an ionic bond as the atoms react. tell what happens to the valence electrons on each atom and how each atom is changed by losing or gaining electrons.

 Each atom in an ionic compound tends either to empty or complete the shell to 8 electrons. So when the number of electrons on the external shell is near 8 , the atom tends to attract electrons to complete the shell giving a positive ion called anion 
Conversely when the number of electrons is small the atom gives these electrons to form a positive ion called a cation