Why is the motion of an electron in a solid different from that in an isolated atom?

(N/A) In an isolated atom,electrons are bound to the nucleus and occupy discrete energy levels defined by the Bohr atomic model. The motion of these electrons is confined to specific orbits around a single nucleus.
When atoms come together to form a solid,they are packed closely. The outer electron orbits of neighboring atoms overlap significantly. This interaction causes the discrete energy levels to split into continuous energy bands.
Consequently,the electrons in a solid are no longer confined to a single atom but can move through the crystal lattice,making their motion fundamentally different from that of an electron in an isolated atom.