Chemistry · Classification of Elements and Periodicity in Properties

Consider the following statements regarding the modern periodic table: (A) Elements having similar outer electronic configurations in their atoms are arranged in vertical columns referred to as groups or families. (B) The period number corresponds to the highest principal quantum number (\( n \)) of the elements in the period. (C) The first period contains 2 elements and the second and third periods contain 8 elements each. (D) There are altogether 18 periods in the modern periodic table. Which of the above statements are correct?

1. All (A), (B), (C) and (D)
2. (A) and (D) only
3. (B), (C) and (D) only
4. (A), (B) and (C) only