Which of the following pair of elements follows Newland’s octave rule -

Which of the following set of elements obeyes Newland’s octave rule -

Which of the following pairs of elements do not follow octave rule

The discovery of which of the following group of elements gave a death blow to the Newlands Law-

Which of the following states that properties of elements are a periodic function of their atomic number''? A) Dobereiner's triads B) Modern periodic law C) Newlands's law of octaves D) Mendeleev's periodic law