To which period of the modern periodic table do these two elements belong

Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be

formed between them and why? 

Answer: Electronic configuration of X (Z=12): 2, 8, 2

Electronic configuration of Y (Z=16): 2, 8, 6 Both these elements belong to third period. 

An ionic bond is formed between X and Y due to transfer of two electrons from X to Y.