Determine whether the following pairs of elements can form ionic compounds.
- sodium and oxygen
- potassium and calcium
- nitrogen and iodine
- manganese and chlorine
- oxygen and calcium
- chlorine and sodium

• Sodium and oxygen

• Manganese and chlorine

• Oxygen and calcium

• Chlorine and sodium

Explanation:

Ionic compounds are formed when a very electronegative element (that is, that has high electronic affinity), comes into contact with a low electronegative or very electropositive element (it is said to have low ionization potential). Thus, an electron transfer takes place, from the electropositive element, remaining with less electrons than its original form and forming a cation, towards the most electronegative, which is left with more electrons than the initial ones, and forms an anion. The difference in charges between the elements causes the union to occur due to the opposite electrostatic forces between them.

This type of bonding occurs between metals with nonmetals, because among these there is a large difference in electronegativity, and the transfer of electrons occurs from metals, which form cations, to nonmetals, which remain as anions.

Therefore, the pairs of elements that can form this type of compound are the pairs that contain a metal and a nonmetal. They are:

• Sodium and oxygen

• Manganese and chlorine

• Oxygen and calcium

• Chlorine and sodium

The other pairs described in the statement (Nitrogen and iodine - Potassium and calcium), are formed by elements of the same family (two nonmetals and two metals, respectively), so there is no significant electronegativity difference so that ionic bonding occurs.