Very confusing Please help

[Alok]

If metals are bonded by sea of electrons then why don't two metal pieces combine when put together?

[studiot]

1 hour ago, Alok said:

If metals are bonded by sea of electrons then why don't two metal pieces combine when put together?

I don't know where you got this but no wonder you are confused.

When atoms join together to form large metallic solids (crystals) their electrons can be categorised into three groups.

The Inner electrons which play no part in anything.
So we don't need to worry about these, they stay with their original atomic nuclei

The bonding electrons, which are shared between atomic nuclei and create the bonding forces.
Because of these forces these electrons only connect neighbouring nuclei.
The forces keep the electrons there, as well as holding the metal lattice together.

Finally, in metals, there are some electrons which become free to roam the entire solid.
They are not attached to any particular nuclei.
These are called conduction electrons and are sometimes referred to as a 'sea of electrons'.
But they play no part in bonding.

 

Does this help?

Edited April 21, 2019 by studiot

[Carrock]

Complementary to studiot's post:

Most metals have a thin layer of oxide which usually prevents any direct metal to metal contact.

If there is any metal to metal contact it's usually a very small area (due to uneven/contaminated surfaces) and any bonds can easily be broken.

I have read that in space, where the above is less significant, accidental welding of two metal surfaces is a significant safety issue.

[gojja]

see, if you are not satisfied by above 2 answers or you want stats:

Look at the electron affinity.

long answer: if metal has to form a bond then essential criteria of the bond formation is that electron "revolve" around 2 atoms (also spend most time in the space between 2 nucleus) and for it to revolve around, it needs to bind strongly, one metal atom has to accomodate it. To accomodate an electron in a metal, one needs to put 45-60 Kj/mol of the energy (for comparison energy available at room temp is somewhat around 2 Kj/mol).

Edited April 12, 2020 by gojja
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