How are the elements arranged on the periodic table?
how are horizontal rows called?
what is the name of vertical columns in a periodic table?
what is the number of periods in a periodic table?
how many columns are there in periodic table?
how are “a” groups called?
what are the examples of transition metals which are belong to b group? ​

polina7snoy    3   14.01.2020 18:18    2