Repulsion Strength

(Polar molecules, Non-polar molecules, etc.)

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Mhun-Jeong Isaac Lee 1B
Posts: 54
Joined: Fri Sep 28, 2018 12:17 am

Repulsion Strength

Postby Mhun-Jeong Isaac Lee 1B » Sat Nov 10, 2018 2:07 am

Hi in the lecture notes it said:
Repulsion strength: lone-lone pair > lone-bonding pair > bonding-bonding pair
Can anyone clarify what this means?

Shubham Rai 2C
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

Re: Repulsion Strength

Postby Shubham Rai 2C » Sat Nov 10, 2018 9:30 am

That list compares the bond strength of the three different interactions that occur around the central atom involving electrons. The list just states that the repulsion between two pairs of lone electrons is greater than the repulsion between a lone pair and a bonded pair. Finally, the interaction between two bonded pair results in the least significant repulsion around the atom.

Albert Duong 4C
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Joined: Fri Sep 28, 2018 12:17 am
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Re: Repulsion Strength

Postby Albert Duong 4C » Sat Nov 10, 2018 3:52 pm

The repulsion strength determines the bond angle and shape of the molecule. In molecules where there are both bond and lone pairs, lone-bonding pair's repulsion strength produces a bond angle between that atoms that is smaller than the bond angle created by an atom For example, a trigonal planar shape has all bonding-bonding pairs so it has a bond angle of 120 degrees, but in a similar shape with a lone on the central atom (like SO2), the bond angle will be slightly less than 120 degrees. Taking it even further, if there are 2 lone pairs this time, the lone-lone pair and lone-bonding pair's repulsion will create an angle that is less than if it was just a lone-bonding pair only. For example, a trigonal pyramidal shape (1 lone pair, 3 atoms) has a bond angle that is less than 109 degrees, but a bent/angular shape (2 lone pairs, 2 atoms) have a bond angle less than even that.

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