Ionic bonds tend to form under two certain criteria and the first is ionic bonds tend to form between metals and nonmetals, so if you have elements and ones a metal and ones a nonmetal an ionic bond is likely to form.
Now the second criteria, is that ionic bonds tend to form between elements with a large difference in electronegativity.
The next lesson: Chemical Reactions, both lessons are included in Practice Tests.The following transcript is provided for your convenience.
The larger the difference in electronegativity, the better the chance ionic bonds are going to form and so if elements meet both each criteria there’s a very good chance they’re very likely to form ionic bonds. Now keep in mind that elements with the highest electronegativity values are in the upper right-hand corner of the periodic table of elements, while those with the lowest are near lower left-hand corner.
You have elements with low elecronegativity down here and elements with high electronegativity up here. Just by knowing those two facts right there, if you see an element on the periodic table, if you just imagine this board as a periodic table and it’s about right here, you just know by where it.s geographically situated on the board, that there is a really good chance that it has a high electronegativity, because its near the top right-hand corner of the periodic table.
Now I have some pairs of elements here and I want to examine these elements to see if they meet these criteria and determine whether or not they’re likely to form ionic bonds. First we have nitrogen and oxygen. Now nitrogen is a nonmetal and then oxygen is obviously a nonmetal, so they’re not likely to form ionic bonds, because it’s now between a metal and a nonmetal, we have two nonmetals here.
Then we have potassium and fluorine and potassium is an alkaline metal and fluorine is a nonmetal so we’ve met the first criteria. We have reaction between a metal and a nonmetal, so we’re doing good so far and then there is a high electronegativity difference here and it’s actually three point two, which is pretty high, so they are likely to form ionic bonds, specifically potassium chloride.
Now here we have barium and sulfur and barium is a metal and then sulfur is a nonmetal, so here we have a metal, and a nonmetal, so we’re doing good so far. They’re likely to form ionic bonds, specifically barium sulfide and then in addition to that, they’re electronegativity difference is mildly large at about one point six.
Now finally we have cesium and tin and cesium is an alkaline metal and I’m sure you can guess that tin is a metal. Here we have two metals interacting with each other, so it’s not between a metal and a nonmetal, so cesium and tin is not likely to form ionic bonds. Notice here the main factor here was that we had two nonmetals and two metals here, but when we have a metal and a nonmetal, they’re likely to form ionic bonds and especially if they have a high electronegativity difference. Hopefully through this short session you have a better understanding of ionic bonds.
The next lesson: Chemical Reactions, both lessons are included in Practice Tests.