What are groups and periods in the periodic table ? Two elements X and Y belong to group 1 and 2 respectively and are in the same period of the periodic table. How do the following properties of X and Y vary ? (i) Size of their atom (ii) Their metallic character (iii) Their valencies in forming oxides (iv) Molecular formula of their chlorides



Groups are the vertical columns in the periodic table which contain elements of the same valency and similar properties....
periods are the horizontal rows which contain elements having the same no of shells.....

i)Y is smaller than X as the no of shells remain the same but nucleus's energy increases
ii)X is more metallic than Y as metallic character increases from right to left in a period...
iii)valency: X - 1, Y - 2
iv)XCl and YCl₂