56. Match List-I with List-II. List-I: (A) Al3+ < Mg2+ < Na+ < F- (B) B < C < O < N (C) B < Al < Mg < K (D) Si < P < S < Cl. List-II: (I) Ionisation Enthalpy (II) Metallic Character (III) Electronegativity (IV) Ionic Radii. Choose the correct answer from the options given below: Option 1: A-IV, B-I, C-III, D-II Option 2: A-II, B-III, C-IV, D-I Option 3: A-IV, B-I, C-II, D-III Option 4: A-III, B-IV, C-II, D-I

Key Periodic Trends to Remember

1. Ionisation Enthalpy (IE)

   • Energy needed to remove the outermost electron.
   • Generally increases left → right across a period and decreases top → bottom down a group, with a few small dips (e.g. $B$ vs. $Be$, $O$ vs. $N$).

2. Electronegativity (EN)

   • Tendency of an atom to pull shared electrons toward itself.
   • Follows the same cross-period trend as IE: increase left → right, decrease down.

3. Ionic Radius

   • Size of an ion.
   • Cations (positive ions) shrink as charge gets more positive ($Na^+ > Mg^{2+} > Al^{3+}$) because protons pull harder on fewer electrons.
   • Anions (negative ions) swell because extra electrons repel each other.
   • Inside an isoelectronic series (same electron count), higher nuclear charge = smaller ion.

4. Metallic Character

   • How easily an element loses electrons and shows properties like malleability, conductivity.
   • Increases right → left across a period and increases top → bottom down a group.

Strategy to Match Lists

• For each row, check if the sequence looks like it follows a known trend.
• Example: If charges keep getting less positive or more negative while size grows, that screams ionic radius.
• If elements are arranged exactly the way ionisation energy normally rises (with the classic $O$ dip after $N$), that row probably represents IE.
• If the list mixes two different periods or groups and simply becomes more metallic (alkali metals at the end), that’s likely metallic character.
• A smooth left-to-right non-metal increase inside the same period hints at electronegativity.

What’s the question?

The question shows four rows of chemical symbols. Each row is already arranged from smallest → largest for some hidden property (like size, stickiness for electrons, etc.). Your job is to guess which hidden property matches each row.

Think of the periodic table like a playground:

• Some kids (atoms) hold on to their marbles (electrons) very tightly (high ionisation energy).
• Some kids really want more marbles (high electronegativity).
• Some are big and bulky when they gain/lose marbles (large ionic radius).
• Some love to give away marbles and act shiny and metallic (metallic character).

The question basically asks: “Which row is which kind of kid?”

Step-by-Step Matching

1. Row A: $Al^{3+} < Mg^{2+} < Na^+ < F^-$
   All four ions are isoelectronic (10 electrons each). The order of size in such a series depends solely on nuclear charge: more protons = smaller ion. Hence this row is Ionic Radii (IV).

2. Row B: $B < C < O < N$
   Across period 2, first ionisation enthalpy increases but with the known exception that $O$ is slightly lower than $N$. The pattern exactly matches. So row B corresponds to Ionisation Enthalpy (I).

3. Row C: $B < Al < Mg < K$
   Moving down and left in the periodic table, elements become more metallic. Therefore the sequence reflects increasing Metallic Character (II).

4. Row D: $Si < P < S < Cl$
   Left → right in period 3, electronegativity rises. Hence this row is Electronegativity (III).

Putting the matches together:

• A → IV
• B → I
• C → II
• D → III

Hence the correct option is Option 3.