Why do electrons form a 'sea' in metallic bonding?

[hasan_researc]

My lecturer writes the following in his lecture notes:
“ In metals electrons dissociate from atoms and form a ‘sea’ of electrons which reduces the repulsion between the metal ions.”

Why do electrons dissociate from atoms in metals?

How does a sea of electrons reduce the repulsion between the metal ions?

 

[sophiecentaur]

1. Why do electrons dissociate from atoms in metals?

2. How does a sea of electrons reduce the repulsion between the metal ions?

1. It's all about the relative binding energy. The energy which binds an outer electron to a metal atom is not any higher than what binds it to the nearby atoms - so the electron can move freely from place to place - as opposed to what often goes on with a non metal or when the adjacent atoms happen not to be metals.

2. The number electrons in the 'sea' is the same as the number of 'extra' protons in all the ion 'cores'. This gives a balance in total charges. Each ion is surrounded by just the same number of + and - charges so no net repulsion. In fact, of course, the nearest electrons are closer than the nearest +ions so there is net attraction (hence the strength of metals).