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.
Electron affinity The energy released when an electron is added to the neutral atom and a negative ion is formed. Electronegativity (Pauling scale) The tendency of an atom to attract electrons towards itself, expressed on a relative scale. First ionisation energy The minimum energy required to remove an electron from a neutral atom in its ground state.