Electron Affinity

Amy Luu 2G
Posts: 105
Joined: Wed Sep 18, 2019 12:19 am

Electron Affinity

In the self check problem 1F.3a, it asks to account for the large decrease in electron affinity between lithium and beryllium. I'm not sure which one has the higher electron affinity. I'm confused on how to tell which atom has a higher or lower affinity and what an electron affinity tells us.

205296774
Posts: 66
Joined: Thu Jul 25, 2019 12:15 am

Re: Electron Affinity

Electron affinity is the likelihood of a neutral atom to gain an electron, making it an anion. Lithium, needing 1 more electron to complete the 2s orbital, has a high electron affinity because it really wants that extra electron to stabilize. Beryllium, on the other hand, has a full 1s and 2s orbital and needs 6 additional electrons to fill the 2p orbital. This process is basically impossible if not completely impossible, so there's a very low likelihood of gaining electrons resulting in a way lower affinity compared to Lithium.

Hope this helps!

AnvitaaAnandkumar_1B
Posts: 56
Joined: Fri Aug 02, 2019 12:15 am

Re: Electron Affinity

Electron affinity describes the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion. It therefore tells us about the ease with which an electron can be added to a gaseous molecule.
The general trend for electron affinity is that it increases as we go from left to right in the periodic table.
In the case of Li and Be however, the electron affinity of Li is much higher than that of Be which can be explained using their electron configurations.
Li :( 1s² 2s¹ )+1e = 1s2 2s2

Be : (1s² 2s²)+1e = 1s2 2s2 2p1

The electron added in the Lithium goes into the 2s sub-shell which being close to the nucleus experiences greater electrostatic force of attraction compared to the one going into the 2p sub-shell of the Beryllium atom which is relatively more diffused( spread out in space ) .

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