An element belonging to Group 1 of the periodic table forms a unipositive ion. In this ionic state, the ratio of the total number of p-electrons to the total number of s-electrons is exactly 2.4 . The atomic number of this element is

Step-by-step solution

Let the element be M . Since it belongs to Group 1, its unipositive ion M⁺ will have the stable electronic configuration of a noble gas. Let us evaluate the ratio of p-electrons to s-electrons for the noble gas cores: For Na ⁺ (Neon core): 1s² 2s² 2p⁶ . Number of s-electrons = 4 , p-electrons = 6 . Ratio = 6 4 = 1.5 For K ⁺ (Argon core): 1s² 2s² 2p⁶ 3s² 3p⁶ . Number of s-electrons = 6 , p-electrons = 12 . Ratio = 12 6 = 2.0 For Rb ⁺ (Krypton core): [ Ar ] 3d¹⁰ 4s² 4p⁶ . Number of s-electrons = 8 , p-electrons = 18