In a galvanic cell, the salt bridge

A list of species having the formula XZ₄ is given below.

XeF₄, SF₄ ,SiF₄, $$BF_4^-$$, $$BrF_4^-$$, [Cu(NH₃)₄]²⁺, [FeCl₄]^2-, [CoCl₄]^2- and [PtCl₄]^2-

Defining shape on the basis of the location of X and Z atoms, the total number of species having a square planar shape is

In an atom, the total number of electrons having quantum numbers n = 4, |m_l| = 1 and m_s = –1/2 is

If the value of Avogadro number is 6.023 $$\times$$ 10²³ mol^-1 and the value of Boltzmann constant is 1.380 $$\times$$ 10^-23 J K^-1, then the number of significant digits in the calculated value of the universal gas constant is