a) What are groups and period in the periodic table? b) Two elements M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary?1) Sizes of their atoms 2) Their metallic characters. 3) Their valencies informing oxides. 4) Molecular formula of their chlorides.

a) What are groups and period in the periodic table? b) Two elements M

1.	a) What are groups and period in the periodic table? b) Two elements M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary?1) Sizes of their atoms 2) Their metallic characters. 3) Their valencies informing oxides. 4) Molecular formula of their chlorides.
Answer» Solution : a) The vertical COLUMNS in the periodic table are called group. The horizontal rows in the periodic table are called periods. b) 1. M and N belong to the same PERIOD but I and II. Therefore N will be smaller than Mas atomic size is decreasing from left to right. 2. M is more metallic than N. Metallic character goes on decreasing from left to right as tendency to lose electrons decreases DUE to decrease in atomic size. 3. Their valencies are 1 and 2 respectively in forming oxides. Valency goes on increasing first and then INCREASES. 4. `MCI, NCI_2`are molecular FORMULAE of their chlorides.