how to remember valency of elements

first you learn the molecular or moiler diagram it is simple to remember the valency of electri=ons

The valencies can be remembered easily.

In higher grades you will be studying the periodic table. There you will be learning about groups. The elements residing in a particular group have same valencies (exception: the p-block elements).

But the concept of periodic table is beyond the scope of your syllabus.

As of now, what you can do is to learn the names of elements till atomic number 20 and try to arrange the electrons present in them into various shells. The electrons present in the outermost shell determine the valency of that element.