It is enough to recite the top 20 in junior high school. Some high school teachers will ask to recite the main group elements and the first transition series elements. If you majored in chemistry in college, you'd better memorize all the periodic table of elements (according to groups), which is helpful to understand the properties of elements.

Personally, I think that the periodic table of elements can be memorized in stages, and the knowledge of junior high school and senior high school is limited, and the use and examination of transitional elements are rare. It is almost enough to know the properties of several commonly used test elements, such as the first series of transition elements and gold, silver and mercury. If you carry too much, it is also a burden to yourself. Personal opinion, if you are particularly interested, you can recite it. After all, there is no harm in studying in advance. )