question_answer 117)

      An element is placed in 2ndgroup and 3rdperiod of the periodic table, burns in presence of oxygen to form a basic oxide. (a) Identify the element. (b) Write the electronic configuration. (c) Write a balanced equation when it burns in the presence of air. (d) Write a balanced equation when this oxide is dissolved in water (e) Draw the electron dot structure for the formation of this oxide.

Answer:

                  (a) Since, the element lies in group 2, it must be an alkaline earth metal. Since, it lies in the third period, it must be magnesium (Mg). (b) Atomic number of Mg is 12, therefore, its electronic configuration is: (c) When Mg burns in the presence of air it forms a basic oxide, MgO. (d) When MgO is dissolved in water it forms magnesium hydroxide (e) Mg has 2 valence electrons [as electronic configuration of] oxygen has6 valence electron [as electronic configuration of]. Electron dot structure for the formation of magnesium oxide.