Why do some substances have more affinity, while some substances have less affinity towards other substances?

Dear student,

Electron affinity is the ability of an atom to gain an electron. It is the energy released in a substance when an electron is attached to a neutral molecule.

Electron affinity depends on the following factors:

1. Atomic size: More is the size of an atom more will be the distance between the nucleus and the incoming electron. Hence the incoming electron will experience less force of attraction towards the nucleus of an atom. Therefore smaller will be the affinity. 

2. Nuclear charge: If the charge on the nucleus increases, the attraction force on the incoming electron increases. Therefore more will be the affinity.

3. Electronic configuration: Atoms that have a stable electronic configuration have a less tendency to accept an electron. Therefore less affinity. 

These are the reason for some substances have more affinity and some having less affinity.


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This due to their atomic structure and valancy.
For eg. Only one ion of chlorine does not possess affinity toward magnesium ion. This is because chlorine ion needs only one positive ion while magnesium is ready to give two ions. Thus such bond is not possible.
This is applicable to other elements too. Every element and atoms have different requirements. So some substances have more or less affinity towards other substances.

I hope you got it.
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