What do the horizontal and vertical columns in the periodic table represent?
Which of the following statement about the modern periodic table is correct?
(a) It has 18 horizontal rows known as periods. (b) It has 7 vertical columns known as periods.
(c) It has 18 vertical columns known as groups. (d) It has 7 horizontal rows known as groups.
What are the horizontal rows and vertical columns in a periodic table known as?
What are horizontal rows and vertical columns in a Mendeleev's periodic table known as?