How many electrons are transferred between the cation and anion to form the ionic bond in one formula unit of each compound? (1 electrons, 2 electrons, 3 electrons, 4 electrons) ?

NaCI

CaS

BaO

KBr

LiF

Here are the solutions:

For NaCl, there would be one electron transferred from the sodium atom, now producing a cation to the chlorine atom resulting in a chlorine anion. Forming ionic bond.

For CaS, there would be 2 electrons transferred from an atom of Ca to S, this can be obtained by simply looking at the ionic charges and or combining capacities of Ca.

For BaO, likewise, 2 electrons that are valence electrons are transferred from Ba to Oxygen.

In the ionic compound of KBr, the atom of K, potassium donated its one valence electron to Br, in need of it to achieve a stable octet, and produce the chemical bond.

Finally, LiF, a single valence electron is transferred from a metal atom of Li to F, for both of the atoms that would form the ionic bond to achieve a stable octet, and or full electron shell.