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Ionic lattices

Hi guys,

I don't understand why mgcl2 forms over mgcl or mgcl3 could someone explain it too me please

Thanks

Mg has 2 electrons in it's outer orbital where as Cl is missing one in it's outer orbital, therefore the Mg will share an electron with each Cl in the molecule. MgCl₂ is therefore more stable.

Reply 2

maissyy

Original post by tree123

Hi guys,

I don't understand why mgcl2 forms over mgcl or mgcl3 could someone explain it too me please

Thanks

In a simple format- Mg is a 2+ ion whereas CL is a 1- ion. Therefore the charges are unequal, in order for them to cancel out and produce a compound you need two CL- ions.

Reply 3

tree123

It says in the textbook something about: the crystal formed from magnesium and chlorine it which that maximizes the lattice energy. What does that mean?

Reply 4

Mockery

Original post by tree123

It says in the textbook something about: the crystal formed from magnesium and chlorine it which that maximizes the lattice energy. What does that mean?

For the reasons already given, the ionic bonding will be stronger in the MgCl₂ molecules and the atoms will be held closer together.

Reply 5

tree123

Original post by Mockery

For the reasons already given, the ionic bonding will be stronger in the MgCl₂ molecules and the atoms will be held closer together.

oh ok, so why is this the most exothermic compared with mgcl and mgcl3

Reply 6

Mockery

Original post by tree123

oh ok, so why is this the most exothermic compared with mgcl and mgcl3

Stronger bonding releases more energy upon breakage.

Reply 7

tree123

Original post by Mockery

Stronger bonding releases more energy upon breakage.

ok why is the formation of mgcl3 for endothermic than the formation of mgcl2? Is it because the bonds are not held as strongly?

Reply 8

charco

Study Forum Helper

Original post by Mockery

Stronger bonding releases more energy upon breakage.

No no no no no!!!!!

Bond breaking is ENDOthermic, it requires energy it does NOT release energy.

Reply 9

Mockery

Original post by charco

No no no no no!!!!!

Bond breaking is ENDOthermic, it requires energy it does NOT release energy.

I stand corrected :wink:

These things begin to slip your mind after a while of not studying much chemisty..

Reply 10

tree123

Original post by charco

No no no no no!!!!!

Bond breaking is ENDOthermic, it requires energy it does NOT release energy.

ok why is the formation of mgcl3 endothermic but the formation of mgcl2 exothermic? Is it because the bonds are not held as strongly?

Reply 11

charco

Study Forum Helper

Original post by tree123

ok why is the formation of mgcl3 endothermic but the formation of mgcl2 exothermic? Is it because the bonds are not held as strongly?

In order to understand the answer you need to do the whole Born Haber cycle for each proposed compound...

Reply 12

Another

Original post by tree123

ok why is the formation of mgcl3 endothermic but the formation of mgcl2 exothermic? Is it because the bonds are not held as strongly?

If you think of it like this:

MgCl2 is already stable with it's noble gas like electron configuration. It's going to repel any more groups of electrons that might try to bond with it - such as those on an incoming Cl atom.

The electrons on MgCl2 and Cl are going to repel each other. If you want these atoms to bond, then you're going to need to put in energy into the system to allow the electrons to overcome the electrostatic repulsions.

Of course, it's also probable that I'm just talking out of my ass here, so don't quote me on it.