question_answer 80)

    Which of the following statements about the modern periodic table is correct? (a) It has 18 horizontal rows known as periods    (b) It has 7 vertical columns rows known as periods (c) It has 18 vertical columns known as groups    (d) It has 7 horizontal rows known as groups

Answer:

                  (c) Modern periodic table has 18 vertical columns, known as groups and 7 horizontal rows, known as periods.