Charles' law is valid when: MCQ with Answer and Explanation

Explanation:
Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond. It increases across a period and decreases down a group. Fluorine, located at the top right of the periodic table (Group 17, Period 2), has the smallest atomic radius and highest effective nuclear charge, giving it the highest electronegativity (3.98 on Pauling scale).

Explanation:
Ionization energy generally increases across a period due to increasing nuclear charge and decreasing atomic size. Among Na, Mg, Al, and Si (Period 3), Si has the highest effective nuclear charge and smallest size, thus requiring the maximum energy to remove the outermost electron from its gaseous state.

Explanation:
Number of half-lives = 24/8 = 3. Fraction remaining = (1/2)³ = 1/8. Activity = 100 × 1/8 = 12.5 counts per minute. Radioactive decay is exponential. After 1 half-life: 50, 2: 25, 3: 12.5. This isotope is used in thyroid treatment.