Explanation

• Amphoteric oxides can react with both acids and bases to form salts and water.
• Tin dioxide (SnO₂) is amphoteric, while CaO is basic and CO₂ is acidic.

Explanation

Transition elements show variable valency because of the involvement of both ns and (n–1)d electrons in bonding.

Normal (main group) elements usually exhibit a fixed valency.

Explanation

Litharge is the mineral form of the inorganic chemical compound lead(II) oxide (PbO)

Appearance: A yellowish or reddish, heavy, earthy solid.

That can be found in earthy coatings and encrustations in the superficial parts of lead deposits.

Also known as lead monoxide or yellow oxide, it is used in industries such as ceramics, glass manufacturing, pigments, and lead-acid batteries. 

 Solubility: It is insoluble in water.

Explanation

The modern periodic table has:

• 7 periods (horizontal rows)
• 18 groups (vertical columns)
• 4 blocks based on electron configuration: s, p, d, f blocks.

Explanation

Moving down the electrochemical series, metals become more reactive and their tendency to gain electrons (reduction potential) decreases.

Simultaneously, their oxidizing ability decreases while reducing ability increases.

Explanation

The law of mass action states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants.

It was formulated by Norwegian chemists C.M. Guldberg and P. Waage in the 19th century.

Explanation

Triatomic molecules can exhibit vibrational, rotational, and translational movements.

So, they show both vibrational & rotational and translational & vibrational motions.

Explanation

The spectrum of He is expected to be similar to that of Li+. 

Both He and Li+ have two electrons, which means their electronic configurations and resulting emission spectra are very similar. 

Explanation

Potassium (K, atomic number 19) has 19 electrons.

Its configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹, which is [Ar] 4s¹ in shorthand.

Explanation

The total number of nodes in an orbital = n – 1, where n = principal quantum number.

For a 4s orbital, n = 4 → nodes = 4 – 1 = 3 nodes.