That is, each electron has a unique address. Two ways of writing e-configs. One is called spectroscopic notation. Other is called the orbital box notation. Electron affinity Atomic Size Size goes UP going down a group.
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.