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

Explanation

To determine which of the given options is not correctly matched, we will analyze each statement step by step.

### Step 1: Analyze Basic Strength of Oxides
The first option states:
**Basic strength of oxides:** `Cs2O > Rb2O > K2O > Na2O > Li2O`

- The basic strength of oxides increases as the size of the cation increases because larger cations have a greater tendency to donate electrons (higher electropositivity).
- The order should be: `Li2O < Na2O < K2O < Rb2O < Cs2O` (least basic to most basic).
- Hence, the order given in this option is incorrect.

### Step 2: Analyze Stability of Peroxides
The second option states:
**Stability of peroxides:** `Na2O2 < K2O2 < Rb2O2 < Cs2O2`

- The stability of peroxides increases with the size of the cation because larger cations form more stable compounds with larger anions (peroxide ion, O2^2-).
- The correct order is: `Na2O2 < K2O2 < Rb2O2 < Cs2O2`, which matches the given statement.
- Thus, this option is correctly matched.

### Step 3: Analyze Stability of Bicarbonates
The third option states:
**Stability of bicarbonates:** `LiHCO3 < NaHCO3 < KHCO3 < RbHCO3 < CsHCO3`

- The thermal stability of bicarbonates increases with the size of the cation because larger cations lead to lower lattice enthalpy and thus higher stability.
- The correct order is: `LiHCO3 < NaHCO3 < KHCO3 < RbHCO3 < CsHCO3`, which matches the given statement.
- Therefore, this option is also correctly matched.

### Step 4: Analyze Melting Point
The fourth option states:
**Melting point:** `NaF < NaCl < NaBr < NaI`

- The melting point of ionic compounds generally decreases with increasing size of the anion when the cation is kept constant.
- The correct order should be: `NaF > NaCl > NaBr > NaI` (highest melting point to lowest).
- Therefore, this order is incorrect as it is stated in the opposite manner.

### Conclusion
From the analysis, we find that:
- Option 1 (Basic strength of oxides) is not correctly matched.
- Option 4 (Melting point) is also not correctly matched.

Thus, the answer to the question is that both Option 1 and Option 4 are not correctly matched.