Arrange these compounds in order of increasing magnitude of lattice energy: KCl, SrO, RbBr, CaO.

Video transcript

Hey everyone. So here it says a range of following compounds. In order of increasing magnitude of lattice energy. Alright so lattice energy we can say takes a portion of columns law which is Q. One times Q two over radius squared. So that's charged one. Times charged two divided by radius squared. Here we're going to basically manipulate this equation and say that this new equation is directly related to it. And here I'm going to say that it's charge A times charge be. So it's first I on second ion multiply together their charges divided by period number of the first ion Plus the period number of the 2nd island. This is just a way of us understanding customs law in much simpler terms to help us rank the lattice energies between different ionic compounds. So if we take a look at the first one we have calcium oxide which is C. A. Two plus and 02 minus. So that would be plus two times -2 in absolute terms divided by Now calcium is in row four period 4. So it's four plus two, oxygen's in road tour period too. So this comes out to be 4/6 which is equal to 2/3 Which is .67. Next we have sodium bromide which is an A. Plus one and B. R minus one. That B plus one times minus one divided by their period numbers sodium and Row three and Row four. Is that the 1/7 Which equals .14. And then finally we have strontium oxide which is S are two plus and 02 minus, So that's plus two times -2 in absolute brackets. Strong teams in row five oxygen's and rode to. Yes, so this comes out to .57. So you want increasing magnitude of lattice energy. So that means basically we want to start out with the smallest one and move our way up to the largest lattice energy. So based on what we see, we see that sodium bromide is the smallest, followed by strong team oxide, and then calcium oxide would be the highest lightest energy. So that would mean that option A is the correct answer. This gives us our order from smallest lightest energy to highest lightest energy.