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.
Trends in Properties of Group 17 (VIIA) Elements. 1  All Group 17 (VIIA) elements have 7 valence electrons (7 electrons in the highest energy level). 2  Atomic radius increases down the Group as successive 'electron shells' (energy levels) are filled. As the atomic radius increases and the electron is further from the nucleus it is less attracted to the nucleus (electron is said to be 'shielded'). 2  Melting point and boiling point increase down the Group as the elements become more metallic in nature.