In this video we'll look at the difference between molecular geometry and electron geometry and these are just two different ways to explain the shape or the geometry of a molecule probably the best way to do this is to look at two examples to see the difference between the molecular geometry and electron geometry in both cases we're .
Interested in the geometry from the perspective of the central atom here we have the nitrogen here from the perspective of the carbon for nh3 we'll start with our lewis structure we have one two three hydrogens and they're bonded to the nitrogen and then we have one lone pair and that lone pair is important because it's pushing down the .
Hydrogen atoms let's look at this in three dimensions so think of the purple as that central nitrogen remember we have three hydrogen atoms one two and you see they spread out to be as far away as they can from each other so right now we have what's called a trigonal planar everything's in one .
Plane don't forget that lone pair when we put the lone pair on it pushes everything down so this gives us a different geometry so the lone pair is important so when we look at the molecular geometry we're not really interested in the lone pair it's still there we're just going to hide it so we take the .
Lone pair and hide it so we still have the same geometry it's still pushing these down but we look at this and we can now name this as trigonal pyramidal it's kind of like a pyramid and we have those three hydrogen atoms on the bottom and they're down there because that lone pair of electrons let's show that lone pair it's still there .
For the electron geometry we take into account the lone pair so now we have what's called a tetrahedral molecular geometry so this lone pair at the top of our tetrahedron so now we say the electron geometry that's tetrahedral let's go back so the key is with the molecular geometry we still have the lone pair .
Pushing things down but when we name it we don't really consider it in the name for electron geometry we have our lone pair so we take our lone pair and these three atoms into account give us our tetrahedral molecular geometry for nh3 let's try this one here ch4 this is methane we have one two three .
Four atoms and no lone pairs let's look at it in 3d so the central atom this is going to be our carbon let's add those four hydrogens one two they're spreading out three the final one four and we don't have any lone pairs since we don't have any lone pairs the molecular geometry and the electron .
Geometry they're the same both are tetrahedral so since there's no lone pairs molecular geometry electron geometry they're the same let's go back so for the electron geometry that takes into account the lone pairs sometimes called the unbonded pairs of electrons for the molecular geometry the lone pairs are still there they influence the .
Geometry but we just don't include those when we write the name this is dr b with the difference between the molecular geometry and the electron geometry thanks for watching