Ionic bonds tend to form under to certain criteria and the first is form
between metals
and nonmetals.
So if you have two elements in one's a metal and one's 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.
So the larger the difference in electronegativity,
The better the chance ionic bonds are going to form. And so
if elements meet both these 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 the lower left-hand corner.
So you have elements with low electronegativity down here
and elements with high electronegativity up here. And so just by knowing those two facts right there.
If you see an element on the periodic table, if you just imagine this board as the periodic table,
and it's about right here you just know by where
it's geographically situated on the board that there's a really good chance
that it has a high electronegativity because it's 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 this criteria and determine whether
or not they are likely to form ionic bonds. So first we have nitrogen and oxygen. Now nitrogen
is a nonmetal.
Then oxygen is obviously
a nonmetal.
So they are not likely
to form ionic bonds because there is not between a metal and a nonmetal we have two nonmetals here.
Then we have potassium and fluorine and potassium is an alkali metal
and fluorine is a nonmetal so we've met the first criteria
we have
reaction here between a metal
and a nonmetal.
So we're doing good so far. And then
there's a
high electronegativity difference here
and it's actually 3.2, which is pretty high so they're likely to form ionic bonds
specifically potassium chloride.
Now here we have barium and sulfur and barium
it's a metal
and then sulfur is a nonmetal.
So here we have a metal a nonmetal we're doing good so far so they're likely to form ionic bonds.
Specifically barium sulfide and then in addition to that their electronegativity
difference is moderately large at about 1.6.
Now finally we have cesium and tin.
And cesium is an alkali metal.
And then I'm sure you can guess that tin is a metal.
So here we have two metals interacting with each other. So it's not between a metal
and a nonmetal. So these cesium and tin is not likely to form ionic bonds.
So 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're have a high electronegativity difference.
So hopefully through this short session you have a better understanding of ionic bonds.