The electron affinity of sodium is lower than that of lithium,
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Question

The electron affinity of sodium is lower than that of lithium, 
while the electron affinity of chlorine is higher than that of 
fluorine. Suggest an explanation for this observation.

Accepted Answer

hey everyone in this example, it states that the electron affinity increases as you go up a group. As an example, selenium has the higher electron affinity than sulfur. However, oxygen above sulfur has a lower electron affinity than sulfur. And we need to explain why this phenomenon happens. So our first step is to recall how our electron affinity is depicted on our periodic table. And so we should recall that electron affinity increases as we go from the left towards the right upward on our periodic table. And so we would also recognize that due to this trend, as we go down our group on our periodic table, we would have a lower electron affinity. Now, simply looking at our electron affinity trend isn't going to explain this phenomenon. So we need to consider our atomic radi Of each of these atoms. So beginning with oxygen we have we have a atomic radius of around 73 m for our adam sulfur. We're going to find a atomic great I Of m. And then for selenium will find an atomic radius of 117 m. So as you can see, the higher our atomic radius as seen in selenium, the greater the electron affinity or the more the more our electron affinity is going to increase for that atom. Now, if you have a smaller atomic radius like oxygen which has the smallest out of this set, we have a lot of repulsive forces. So we have a high amount of repulsive forces between our electrons that are entering the p orbital's And this is going to decrease the electron affinity of our adam. And so overall we can conclude for answer that oxygen's small atomic radius or atomic great I well increase the repulsive forces between electrons entering the P orbital's, which is where all of these atoms are located at on our periodic table. Over here, we recall that the P orbital is around this area and therefore causing electron affinity. Two be less eggs are thermic, and so these atoms are going to want to have a smaller value for their electron affinity if their radius is small. And so our final answer is this boxed in explanation right here. So if you have any questions, please leave them down below and I will see everyone in the next practice video.

The electron affinity of sodium is lower than that of lithium, while the electron affinity of chlorine is higher than that of fluorine. Suggest an explanation for this observation.

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