Which best describes how an ionic bond forms?
a. one atom pulls an electron from another atom.
b. two atoms both lose an electron.
c. two molecules share an electron.
d. two atoms share valence electrons

Option (A) is the correct answer.

Explanation:

Ionic bonds are the bonds that are formed by transfer of electrons from one atom to another.

For example, NaCl is an ionic compound because sodium donates its one valence electron to the electronegative chlorine atom.

Thus, we can conclude that one atom pulls an electron from another atom best describes how an ionic bond forms.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.