Which of the following statements are correct?
1. There are 18 elements in the fourth and fifth period.
2. The seventh period is incomplete with 33 elements.
3. The sixth period has 32 elements.

The law of Octaves' was proposed by:

A. Johann Dobereiner

B. Alexander Newlands

C. Lothar Meyer

D. Dmitri Mendeleev

Periodic classification of elements can be done on the basis of electronic configuration and is used to examine the

A. Periodic trends in physical properties of elements

B. Periodic trends in chemical properties of elements

C. Both A and B

D. None of the above

Which of the following resembles the 10^th element in Newland's periodic classification?

A. third

B. ninth

C. fourth

D. first

Johann Dobereiner gave the idea of trends among physical and chemical properties of several groups of three elements, the relationship referred to as

A. law of Triads

B. law of Dobereiner

C. law of Octaves

D. law of Duet