Question

Which of the following statements is INCORRECT ?
A. Generally the radius trend and the ionization energy trend across a period are opposites.
B. metallic and covalent radii of potassium are `2.3A` and `2.03A` respectively.
C. Amongst `Li^(-),Be^(-)` and `C^(-),Li^(-)` is least stable ion.
D. Atomic and ionic radii of Niobium and Tantalum are almost same

Answer 1

Correct Answer - 3
`(1)` Across the period, size decreases as electrons are added in the same shell and nuclear charge increases by one unit for additon of each successive element.
In contrary , the ionization energy increases as size of atom decreases and nuclear charge increases.
`(2) r_("metallic")gtr_("covalent")(` covalent bond formation involves the overlapping of orbitals).
`(3)._(3)Li^(-)-1s^(2)2s^(2)` completely filled stable configuration , so more stable.
`._(4)Be^(-)-1s^(2)2s^(2)2p^(1)`
`._(5)B^(-)-1s^(2)2s^(2)2p^(2)`
`._(6)C^(-)-1s^(2)2p^(3)` half filled stalbe stable configuration , so more stable.
`(4)` Due to lanthanide contraction.