Explain why sodium loses one electron and chlorine gains one electron in three or more sentences.

Sodium and chloride form an ionic bond. Therefore the sodium atom loses one electron from its outer shell and the chlorine atom gains one electron. As this happens, the electron is transferred from the sodium atom to the chloride atom and so both atoms become ionic and have a full outer shell.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).

particle   p is an electron and particle q is a neutron