04-11-2018, 10:36 AM

Hi,

Short version of question: in the video below at 2:25 - why is x √2 and not 1 when regarding the coordinates (√2,1,0) - I thought the hypotenuse of the triangle should be √2?

https://www.youtube.com/watch?v=2UTr46btzaY

Long version:

I've been struggling for sometime with understanding why bond angles in tetrahedral structured molecules are ideally 109.5 degrees.

I've looked at various proofs including a few involving drawing tetrahedrons in boxes but the closest I've come to understanding is the khan academy explanation below:

https://www.youtube.com/watch?v=2UTr46btzaY

I like the way the tetrahedron is lined up against the axis and get the use of Pythagoras and assuming equidistance between all points, however I don't understand how the coordinates of the first example point are obtained (2:25 mins in) - I see the right angled triangle as drawn and understand that √2 will be involved as the other two sides are length 1 and a^2+b^2=c^2

But.. why is x √2 and not 1 when regarding the coordinates (√2,1,0) - I can see y would be 1 and z would be 0

A maths question really but heavily linked to chemistry..

Thanks for looking

Short version of question: in the video below at 2:25 - why is x √2 and not 1 when regarding the coordinates (√2,1,0) - I thought the hypotenuse of the triangle should be √2?

https://www.youtube.com/watch?v=2UTr46btzaY

Long version:

I've been struggling for sometime with understanding why bond angles in tetrahedral structured molecules are ideally 109.5 degrees.

I've looked at various proofs including a few involving drawing tetrahedrons in boxes but the closest I've come to understanding is the khan academy explanation below:

https://www.youtube.com/watch?v=2UTr46btzaY

I like the way the tetrahedron is lined up against the axis and get the use of Pythagoras and assuming equidistance between all points, however I don't understand how the coordinates of the first example point are obtained (2:25 mins in) - I see the right angled triangle as drawn and understand that √2 will be involved as the other two sides are length 1 and a^2+b^2=c^2

But.. why is x √2 and not 1 when regarding the coordinates (√2,1,0) - I can see y would be 1 and z would be 0

A maths question really but heavily linked to chemistry..

Thanks for looking