Which pair of elements if most apt to form an ionic compound with each other? (a) calcium, sodium(b) oxygen, fluroine(c) barium, bromine(d) sulfur fluorine

(C) Barium, bromine

Explanation:

Ionic compounds are the compounds which are formed between two oppositely charged ions held together by strong electrostatic forces.

The positively charged ion is known as cation whereas the negaticvely charge ion is known as anion.

Metals form cations because they lose electrons to gain stability.

Nonmetals form anions because they gain electrons to gain stability.

Thus, the metal nonmetal combination generally forms ionic compound which is given by option C  in which barium is the metal and bromine is the nonmetal.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

the answer is na (sodium)