Electrons are added further from the nucleus, there is less attraction. Size goes DOWN going across a period. Trends in ion sizes are the same as atom sizes. This is why ox. Metals lose electrons more easily than nonmetals.
Metals are good reducing agents.
Nonmetals do not lose electrons. IE decreases down a group Because size increases. Reducing ability generally increases down the periodic table. A few elements GAIN electrons to form anions. Electron affinity is the energy involved when an anion loses an electron.