The half-life of a radioactive isotope is 10 days. What fraction of the original sample remains after 30 days? MCQ with Answer and Explanation

Explanation:
The enhanced greenhouse effect causing global warming is mainly due to rising CO₂ levels from fossil fuel combustion, deforestation, and industrial processes. Other GHGs like CH₄, N₂O, CFCs also contribute. Oxygen and nitrogen are not greenhouse gases. Argon is noble gas, inert. The atmospheric CO₂ has increased from ~280 ppm (pre-industrial) to over 420 ppm. This leads to climate change, sea level rise, and extreme weather.

Explanation:
Carbon has 4 valence electrons; it forms four covalent bonds by sharing electrons to achieve octet. It does not form ionic bonds easily due to high ionization energy and electron affinity.

Explanation:
Graham's law: r_A / r_B = √(M_B / M_A). 4 = √(64 / M_A) → square both sides: 16 = 64 / M_A → M_A = 64/16 = 4 g/mol (Helium).