When a sodium atom transfers an electron to a chloride atom, the result is the formation of two ions: a sodium ion (Na+) and a chloride ion (Cl-). This process is known as ionic bonding. The sodium ion has a positive charge because it has lost an electron, while the chloride ion has a negative charge because it has gained an electron. The opposite charges of the ions attract each other, forming a stable compound called sodium chloride (NaCl).