Who proposed the atomic theory of matter, stating that all matter is composed of indivisible atoms? MCQ with Answer and Explanation

Explanation:
Reactivity series orders metals according to their ease of oxidation—i.e., losing electrons to form cations. At the top (K, Na) are strong reducing agents, reacting vigorously with water and acids; at the bottom (Au, Pt) are noble metals, resistant to corrosion. The series helps predict displacement reactions and extraction methods. Mnemonic: 'Please Stop Calling Me A Cute Zebra...' etc.

Explanation:
Methane is CH₄, the simplest alkane with one carbon atom bonded to four hydrogen atoms. The series general formula is CₙH₂ₙ₊₂. For n=1, H=4. CH, CH₂, CH₃ are not stable neutral molecules; they are fragments (methyl radical etc.). Methane is a major component of natural gas and biogas.

Explanation:
Atomic radius decreases across a period due to increasing nuclear charge. Sodium (Na) is the first element in period 3, thus it has the largest atomic radius. Argon (noble gas) has the smallest (though noble gas radii are van der Waals and larger than covalent, but still trend is decreasing). For metals, Na > Mg > Al; non-metals further smaller.