Question

In which of the following, the elements Al, B, Mg and K are correctly arranged in the increasing order of their metallic character?

• A. \(B\lt Al\lt Mg\lt K\)
• B. \(B\lt Mg\lt Al\lt K\)
• C. \(Al\lt Mg\lt K\lt B\)
• D. \(B\lt Mg\lt K\lt Al\)

Hint:

Metallic character increases towards the left and downward in the periodic table because atoms lose electrons more easily in those directions.

Answer 1

The Correct Option is A

Step 1: Locate each element in the periodic table.
B (Boron): Period 2, Group 13. Al (Aluminium): Period 3, Group 13. Mg (Magnesium): Period 3, Group 2. K (Potassium): Period 4, Group 1.
Step 2: Recall the trend for metallic character.
Metallic character increases going DOWN a group (more electron shells, easier to lose electrons) and increases going from RIGHT to LEFT across a period (fewer protons pulling on valence electrons).
Step 3: Compare B and Al (same group, Group 13).
Al is below B in Group 13, so Al is more metallic than B. Order so far: B < Al.
Step 4: Compare Al and Mg (same period, Period 3).
Mg is in Group 2 (left of Al in Group 13). Going left across a period increases metallic character, so Mg is more metallic than Al. Order: B < Al < Mg.
Step 5: Place K in the order.
K is in Period 4, Group 1 - the leftmost main-group element in Period 4. It has the lowest ionization energy and highest metallic character among these four. So K is most metallic.
Step 6: Write the final increasing order.
B (non-metal) < Al (weakly metallic) < Mg (alkaline earth) < K (alkali metal).
\[ \boxed{B < Al < Mg < K} \]