Aqua regia is a mixture of: MCQ with Answer and Explanation

Explanation:
SO₂ from burning coal and NOₓ from vehicles form H₂SO₄ and HNO₃ in rain. CO₂ forms weak carbonic acid (normal rain pH ~5.6). Ammonia is basic and neutralizes acidity.

Explanation:
Valence electrons are the electrons in the outermost shell. Configuration 2,8,2 means K=2, L=8, M=2. The outermost shell M has 2 electrons, so valency is 2, typical of Group 2 metals (Mg). These atoms lose 2 electrons to form M²⁺. The number of valence electrons determines the group in the periodic table. Elements with 2 valence electrons belong to Group 2 (alkaline earth metals).

Explanation:
Neutron has mass approximately equal to proton (1.675 × 10⁻²⁷ kg) and no electric charge. Proton mass ~1.673 × 10⁻²⁷ kg, positive charge. Electron mass ~9.11 × 10⁻³¹ kg, negative charge. Positron is the antiparticle of electron, same mass, positive charge. Neutron's neutrality makes it important for nuclear stability.