Which pair of elements is most likely to form an ionic bond?
a) nitrogen and oxygen
b) carbon and hydrogen
c) sulfur and oxygen
d) calcium and oxygen
Solution 1 SAQ Step 1 of 5 The ionic bond can be formed between elements having high difference between their Electronegativity values, The electronegativity for each element can be read on the periodic table. Usually, if the Electronegativity difference (EN) between the elements involved in a bond is greater than 1.9, we can consider that they are linked together by an ionic bond. Since electronegativity is a periodic property (increases from left to right in the periodic table, decreases from the top to the bottom of the periodic table), if you don’t remember what is the exact electronegativity value of each elements, it will be sufficient give a look to the position of the elements to estimate their Electronegativity difference. Elements too far apart (example: a metal and a non-metal) will give an ionic bond; elements very close together in the periodic table (they could even belong to the same group) will form different kinds of bonds. We are going to demonstrate the correct answer is the letter d) Let’s try to solve for every combination of the exercise Step 2 of 5 Letter a) Nitrogen belongs to the Group V A of the periodic table, Oxygen to the group VI A. They are both non metals. Moreover, Nitrogen has an electronegativity value of 3.0 ; Oxygen has an electronegativity value of 3.5. The EN= 3.5 -3.0 = 0.5. Thus the bond between Nitrogen and Oxygen can’t be ionic. Step 3 of 5 Letter b) Carbon belongs to the Group IV A of the periodic table, Hydrogen to the group I A. Even if there is a substancial difference in their position in the periodic table, they must be considered both as non metals. Moreover, Carbon has an electronegativity value of 2.5 ; Oxygen has an electronegativity value of 2.1. The EN= 2.5 - 2.1= 0.4. Thus the bond between Carbon and Hydrogen can’t be ionic.