Write the number of periods the Modern Periodic Table has. State the changes in valency and metallic character of elements as we move from left to right in a period. Also state the changes, if any, in the valency and atomic size of elements as we move down a group.
The modern periodic table has seven periods.
On moving from left to right in the periodic table, the metallic character of elements decreases, while the valency first increases from 1 to 4 and then decreases to 0 (zero).
On moving down the group, the atomic size of the elements increases, but the valency remains the same.