Grade 11 : Chemistry - Periodic Table (Set 2)

Explanation: Henry Moseley established that the physical and chemical properties of elements are periodic functions of their atomic numbers ($Z$), leading to the Modern Periodic Law.

Explanation: The third period fills $3s$ and $3p$ subshells. Total electron capacity is $2 + 6 = 8$, so there are 8 elements (Sodium to Argon).

Explanation: Group 17 elements (F, Cl, Br, I, At) form salts when reacted with metals and are named Halogens (salt-formers).

Explanation: Group 2 elements have 2 valence electrons in their outermost s-orbital, giving the general valence configuration $ns^2$.

Explanation: Fluorine ($F$) is the most electronegative element with an assigned value of 4.0 on the Pauling scale due to its small size and high nuclear charge.

Explanation: Moving across a period, effective nuclear charge increases while the principal quantum number $n$ remains constant, pulling electrons closer and decreasing atomic radius.

Explanation: Electronic configuration of Iron ($Z=26$) is $[Ar] 3d^6 4s^2$. Since the last electron enters the $3d$ subshell, it is a d-block element.

Explanation: Moving down a group, atomic size and inner electron shielding increase, making outermost electrons easier to remove and decreasing ionization enthalpy.

Explanation: Chlorine (Cl) has a more negative electron gain enthalpy than Fluorine ($F$) because Fluorine's small $2p$ shell experiences strong inter-electronic repulsions.

Explanation: The p-block is unique because it accommodates metals (e.g., Al), non-metals (e.g., C, O, N), and metalloids (e.g., Si, Ge).

Explanation: The long form of the periodic table consists of 7 horizontal rows called periods and 18 vertical columns called groups.

Explanation: For isoelectronic species, higher nuclear charge ($Z$) pulls electrons closer. $Mg^{2+}$ has $Z=12$, the highest among the choices, giving it the smallest ionic radius.

Explanation: Li (Group 1, Period 2) exhibits a diagonal relationship with Mg (Group 2, Period 3) due to similar ionic radii and ionic charge/radius ratios.

Explanation: $Z=12$ is Magnesium ($1s^2 2s^2 2p^6 3s^2$). It readily loses 2 valence electrons to achieve noble gas configuration, exhibiting an oxidation state of +2.

Explanation: $Al_2O_3$ reacts with both acids and bases to yield salt and water, making it an amphoteric oxide.

Explanation: Copper ($Z=29$) has an anomalous configuration $[Ar] 3d^{10} 4s^1$ due to the extra stability of fully filled d-orbitals.

Explanation: Ionization enthalpy is measured for an isolated gaseous atom in its ground state to eliminate intermolecular force influences.

Explanation: Group 16 elements (O, S, Se, Te, Po) are called chalcogens, meaning ore-forming elements.

Explanation: Helium (He) has the smallest atomic size and a stable $1s^2$ closed shell, giving it the highest first ionization enthalpy among all known elements.

Explanation: The f-block comprises 4f-series (Lanthanides, Ce to Lu) and 5f-series (Actinides, Th to Lr), each containing 14 elements.