Write the number of period the modern periodic table has. How do the valency and metallic character of elements vary on moving from left to right in a period ? How do the valency and atomic size of elements vary down a group ?

Explanation

There are 7 horizontal rows known as periods, that the modern periodic table has.
In periods, the number of valence electrons increases from left to right and due to decrease in atomic size, the force of attraction between the valence electrons and the nucleus increases. Metallic character decreases along the period due to decrease in tendency to lose electrons.
Atomic size generally increases from top to bottom in a group due to the addition of a new shell i.e., number of shells goes on increasing down the group.