Toss the beef with 1/2 teaspoon each salt and pepper. Heat the oil in a pressure cooker over medium-high heat. Add the beef and cook, stirring occasionally, until browned on all sides, about 4 minutes.Add the onions and cook, stirring frequently, until the onions soften and begin to brown, about 4 minutes.eat the oil in a pressure cooker over medium-high heat. Add the beef and cook, stirring occasionally, until browned on all sides, about 4 minutes. Add the onions and cook, stirring frequently, until the onions soften and begin to brown, about 4 minutes.
Thus, metals have positive electron affinities. In the Periodic Table, electron affinity increases (becomes more negative) from left to right in a period. Electron affinity decreases from top to bottom in a Group.
Periodic trends - Electron affinity. 1  The electron affinity of an atom can be described either as the energy released by an atom when an electron is added to it, or conversely as the energy required to detach an electron from a singly charged anion.