Which of the following statements are incorrect regarding Mandleev’s periodic table?
(a) Mandleev considered compounds formed by element with oxygen and hydrogen.
(b) In the table Ni is placed before Co.
(c) Eka-silicon in Mandleev’s periodic table is gallium.
(d) The properties of elements are the periodic function of their atomic masses.
(1) Only (b)
(2) Only (c)
(3) Both (b) & (c)
(4) Both (a) & (d)