Question

Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.
EXPLAIN your answer please :)

Li or K

Cl or C

C or N

Li or F

Answer 1

a)K
b)cl
c)N
d)F

Answer 2

Electron affinity measures the attraction between an atom and an added electron. In other words, it describes how easily an atom gains an electron andbecomes an ion.
The more negative an electron's affinity, the greater the attraction of the atom for an electron.

Li has a greater affinity than K because it's affinity is -60kJ/mol, which is more negative than K's -48kJ/mol

Cl has a greater affinity than C because it's affinity is -349kJ/mol, which is more negative than C's -122kJ/mol

C has a greater affinity than N because it's affinity is -122kJ/mol, which is more negative than N's positive affinity. When an affinity is positive, itmeans you actually need to insert energy to have that atom bond with an electron! This means it's electron affinity is veeery low.


F has a greater affinity than Li because it's affinity is -328kJ/mol, which is more negative than Li's -60kJ/mol

Now, you may be wondering where I got these numbers from? How can you tell the electron affinity of an element. Well, they are quite random actually,though they have a biiit of a pattern. The further to the right you go on the periodic table, the higher the electronegativity gets. The exception to thisare the groups (families) 2A, 5A and 8A(noble gases) which are usually much lower in electronegativity than the surrounding atoms.

As for the exact figures, there is no rule, sorry =(
You'll have to consult a textbook, website or manual to be sure when comparing electron affinities =)