kind of need some guidance with "PART C" below:

A) The bond angles in CH4 are 109.5degrees, while the bond angles in NH3 are 107 degrees.
Based on this information, which type of repulsion must be greater:

BP-BP

LP-BP

((((for this part I got: "LP-BP" as the correct answer))))

&

B) The bond angles in NH3 are 107degrees, while the bond angles in H2O are 105degrees. Based on this information, which type of repulsion must be greater?

LP-BP

LP-LP

((((for this part I got "LP-LP" as the correct answer))))

What I need help with, however, is:

C) Based on your answers to Parts A and B, arrange the three types of repulsion in order of increasing magnitude:

i) LP-BP < BP-BP < LP-LP

ii)BP-BP < LP-LP < LP-BP

iii) LP-LP < LP-BP < BP-BP

iv) BP-BP < LP-BP < LP-LP

----I think that the correct order should be: BP-BP < LP-BP < LP-LP
Is this correct??? Bonded-Bonded pairs sould not have a lot of repulsion if there are no lone pairs, correct??? Then as I asnwered in Part A - LP-BP & then as I asnwered in Part B - LP-LP???

& how can I tell/know for certain??? Any help is HUGELY appreciated!!

(BP = bonded pair LP = lone pair)

I got the answer correct!!...It was BP-BP < LP-BP < LP-LP

right. The answer I posted earlier is the opposite of what you have BUT I labeled it differently; i.e., from high to low.

To determine the order of increasing repulsion, we need to compare the repulsion caused by different types of electron pairs (bonded pairs and lone pairs).

In Part A, you correctly identified that the type of repulsion that must be greater is LP-BP. This is because a lone pair (LP) exerts a stronger repulsion than a bonded pair (BP).

In Part B, you correctly identified that the type of repulsion that must be greater is LP-LP. This is because two lone pairs (LP-LP) experience the strongest repulsion compared to other combinations of electron pairs.

Now, let's use this information to determine the correct order of increasing repulsion for Part C:

i) LP-BP < BP-BP < LP-LP: This order is incorrect because LP-LP should be the greatest, not the least.

ii) BP-BP < LP-LP < LP-BP: This order is correct. As you reasoned, bonded-bonded pairs (BP-BP) have minimal repulsion if there are no lone pairs. Then, LP-LP repulsion is the strongest, followed by LP-BP repulsion.

iii) LP-LP < LP-BP < BP-BP: This order is incorrect because LP-BP should be the greatest, not the least.

iv) BP-BP < LP-BP < LP-LP: This order is correct. As you reasoned, bonded-bonded pairs (BP-BP) have minimal repulsion if there are no lone pairs. Then, LP-BP repulsion is greater, followed by LP-LP repulsion.

Therefore, the correct order of increasing repulsion for Part C is: BP-BP < LP-BP < LP-LP. Your answer is correct.