The S Block Elements

The correct answer is (D) : Na₂B₄O₇

Aqueous solution of borax is buffer whose PH ≃ 9
is borax and when it is treated with water, it forms and NaOH. NaOH is a strong base and is a weak acid. As aqueous solution of boric acid is alkaline, hence it is basic in nature.

The correct answer is (D) : Be
Beryllium does not give flame test because of its small size and high ionization energy the energy of flame is not sufficient to excite the electrons to higher energy level.

The correct answer is (A) : Washing soda only

ion is present only in washing soda.
Baking soda →
Washing soda →
Caustic soda →NaOH

The correct answer is (B) : A-IV, B-II, C-I, D-III
(A) Cl₂O₇ → Acidic
(B) Na₂O → Basic
(C) Al₂O₃ → Amphoteric
(D) N₂O → Neutral
Oxides of metals are basic in nature whereas oxides of non metals are acidic in nature. N₂O is a neutral oxide.

When lithium nitrate (LiNO₃) and sodium nitrate (NaNO₃) are heated, they decompose into different products due to their distinct positions in the periodic table and chemical reactivity.

1. For lithium nitrate:
   • The decomposition reaction of lithium nitrate is as follows:

• This reaction indicates that lithium nitrate decomposes to form lithium oxide (Li₂O), nitrogen dioxide (NO₂), and oxygen (O₂) gases upon heating.

1. For sodium nitrate:
   • The decomposition reaction of sodium nitrate is as follows:

• This reaction shows that sodium nitrate decomposes to form sodium nitrite (NaNO₂) and oxygen (O₂). Sodium nitrite is a solid compound.

Therefore, the correct answer is that upon heating, lithium nitrate gives lithium oxide (Li₂O) and sodium nitrate gives sodium nitrite (NaNO₂).

Conclusion: The correct option is Li₂O and NaNO₂.

The correct answer is (C) : CaO
Since, oxides of metals are basic in nature. Hence CaO is a basic oxide
SO₃ and SiO₂ are acidic oxides and Al₂O₃ is a amphoteric oxide.

The melting points of alkali metals decrease down the group. This trend is explained by the nature of metallic bonding:

• Metallic bonding arises from the electrostatic attraction between the positive metal ions and the sea of delocalized electrons.
• As the atomic size increases down the group, the outermost electron is held less strongly.
• This leads to weaker metallic bonding and, consequently, a lower melting point.

Melting Points of the Given Alkali Metals:

• Sodium (Na): 98°C
• Potassium (K): 64°C
• Rubidium (Rb): 39°C
• Cesium (Cs): 29°C

Observation:

Among the given alkali metals, cesium (Cs) is the largest atom, leading to the weakest metallic bonding and the lowest melting point.

Conclusion:

Final Answer: Cs has the least melting point.