The elements of group 1 describe, more clearly than any other group of elements, the effects of increasing the size of atoms or ions on the physical and chemical properties.The chemical and physical properties the elements are closely related to their electronic structures and sizes.These metals are highly electropositive and thus form very strong bases, and have quite stable oxo-salts, In the manufacturing of sodium hydroxide chlorine and sodium carbonate, the sodium chloride is used as starting material.
Which is not correctly matched ?
(1)Basic strength of oxides , `Cs_2OltRb_2OltK_2OltNa_2OltLi_2O`
(2)Stability of peroxides , `Na_2O_2 lt K_2O_2 lt Rb_2O_2 lt Cs_2O_2`
(3)Stability of bicarbonates , `LiHCO_3 lt NaHCO_3 lt KHCO_3 lt RbHCO_3lt CsHCO_3`
(4)Melting point , NaF < NaCl < NaBr < Nal

Options

A. 1 and 4
B. 1 and 3
C. 1 and 2
D. 2 and 3

Answer

A

Explanation

Basic strength of the oxides increase in the order `Li_2O` lt `Na_2O` lt `K_2O` lt `Rb_2O` lt `Cs_2O`.The increase in basic strength is due to the decrease in I.E. and increase in electropositive character. The melting points of the halides decrease in the order NaF gt NaCl gt NaBr gt NaI, as the size of the halide ion increases. The decrease in melting point is due to increase in the covalent character with increase in the size of anion according to Fajan's rule.