The correct answer is Na, Sodium metal Electron affinity is the change in energy of a neutral atom or molecule when an electron is added to the atom to form a negative ion. In simple terms it is the likelihood of gaining an electron. Nonmetals like to gain electrons to form anions to have a fully stable electron shell, while metals lose electrons to form cations and have a stable electron shell. Argon atom for example in the gas phase; gives off energy when it gains an electron to form an ion of Argon.
