Group 14 Elements

Let's evaluate each of the given statements related to group 14 elements:

1. Statement (A): Covalent radius decreases down the group from C to Pb in a regular manner.
   This statement is incorrect. Generally, covalent radii increase down the group as additional electron shells are added. However, the increase is irregular due to the presence of d and f orbitals in heavier elements, particularly in lead (Pb).
2. Statement (B): Electronegativity decreases from C to Pb down the group gradually.
   This statement is generally true as moving down the group, the electronegativity tends to decrease due to increased atomic size and shielding effect. However, elements like lead (Pb) might show deviations due to relativistic effects.
3. Statement (C): Maximum covalence of C is 4 whereas other elements can expand their covalence due to the presence of d orbitals.
   This statement is correct. Carbon, being a second-period element, does not have d orbitals and can form a maximum of four covalent bonds. The heavier elements in group 14, like silicon (Si) and others, can use their d orbitals to expand their covalence beyond four.
4. Statement (D): Heavier elements do not form π-π bonds.
   This is correct. Heavier elements in group 14, such as silicon (Si), germanium (Ge), tin (Sn), and lead (Pb), do not commonly form stable π-π bonds due to their larger atomic size and effective nuclear charge, which makes overlap less effective.
5. Statement (E): Carbon can exhibit negative oxidation states.
   This is correct. Carbon can show negative oxidation states, such as in carbides (e.g., CaC₂), where the oxidation state of carbon is -1.

Based on the evaluation:

• Statement (A) is incorrect because covalent radii increase down the group.
• Statement (B) is generally true but not as gradual due to relativistic effects in heavier elements.
• Statement (C) is correct.
• Statement (D) is correct.
• Statement (E) is correct.

Hence, the correct set of statements is (C), (D), and (E) Only.

The correct answer is:

• (C), (D), and (E) Only

The question asks us to identify the amphoteric oxides among the given options of group 14 element oxides. Amphoteric oxides are those that can react both as acids and bases. To solve this, we need to consider the properties of each given oxide.

1. : This is a neutral oxide, not amphoteric.
2. : Silicon dioxide is acidic and not amphoteric.
3. : Germanium monoxide is a basic oxide, not amphoteric.
4. : Germanium dioxide is amphoteric.
5. : Tin dioxide is amphoteric as it can react with both acids and bases.
6. : Lead dioxide is amphoteric, as it can also react with acids and bases.

Based on the above analysis, the oxides that are amphoteric from the given group 14 elements are and . Therefore, the correct answer is:

These oxides ( and ) can react with both acids, such as hydrochloric acid, and bases like sodium hydroxide, exhibiting their amphoteric behavior.