The electronic configurations of three elements X, Y and Z are X -2, 8; Y – 2, 8, 7 and Z – 2, 8, 2. Which of them is a metal and a non-metal?
Y is a non-metal. X and Z are metals.
Explanation: Y is non-metal because it has 7 valence electrons. It can gain one electron to achieve stable electronic configuration.
X (2,8) and Z (2,8,2) are metals because their outermost shells are completely filled.