# Quick polarisation questionWatch

#1
Bit confused because my notes say two different things I know that the larger the negative ion is, the more easily polarised it is, but what effect does the charge have? One part of my notes says the higher the charge, the more easily polarised it is as there would be more electrons and thus electron repulsion? The other part of my notes says that negative ions are more easily polarised if they have a smaller charge (as there's a lower nuclear charge and thus lower force of attraction to nucleus).

Could someone let me know which of my points is right, cheers .
0
4 years ago
#2
(Original post by BBeyond)
Bit confused because my notes say two different things I know that the larger the negative ion is, the more easily polarised it is, but what effect does the charge have? One part of my notes says the higher the charge, the more easily polarised it is as there would be more electrons and thus electron repulsion? The other part of my notes says that negative ions are more easily polarised if they have a smaller charge (as there's a lower nuclear charge and thus lower force of attraction to nucleus).

Could someone let me know which of my points is right, cheers .
OK..... within a group polarisability increases with atomic number. This doesn't hold across periods as it decreases moving right across the period. As you increase the principle quantum number of the valence shell, the electrons are becoming more weakly bound and their orbits more easily distorted by an electric field (i.e. a dipole from a nearby molecule)

This idea that more weakly bound electrons are more easily distorted in their orbits can be applied to the differences in the polarisability of ions. Negative ions have more weakly bound valence electrons than the corresponding atom or cation so the polarisability will increase with increasing negative charge for a given element.
0
#3
(Original post by JMaydom)
OK..... within a group polarisability increases with atomic number. This doesn't hold across periods as it decreases moving right across the period. As you increase the principle quantum number of the valence shell, the electrons are becoming more weakly bound and their orbits more easily distorted by an electric field (i.e. a dipole from a nearby molecule)

This idea that more weakly bound electrons are more easily distorted in their orbits can be applied to the differences in the polarisability of ions. Negative ions have more weakly bound valence electrons than the corresponding atom or cation so the polarisability will increase with increasing negative charge for a given element.
I understood a bit of this... This seems a bit beyond my level though (Just started AS (year 12)). As a general rule, would I be correct in saying as the negative charge increases, the polarisability increases? And would this be correct: As the nuclear charge on the ion increases it becomes less polarisable as there would be a stronger force of attraction between the nucleus and outer electrons?
0
4 years ago
#4
(Original post by BBeyond)
I understood a bit of this... This seems a bit beyond my level though (Just started AS (year 12)). As a general rule, would I be correct in saying as the negative charge increases, the polarisability increases? And would this be correct: As the nuclear charge on the ion increases it becomes less polarisable as there would be a stronger force of attraction between the nucleus and outer electrons?
yes
1
#5
(Original post by JMaydom)
yes
Thank you!
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