Question

In which of the following options, elements are correctly arranged in the increasing order of their atomic radius?

• A. Si < P < Na < N < F
• B. Na < Si < P < N < F
• C. F < N < P < Si < Na
• D. N < F < Si < P < Na

Hint:

Remember the general trend: Radius increases down-left. Helium is smallest, Francium/Cesium is largest.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:

Atomic radius trends in the periodic table:
1. Across a Period (Left to Right): Atomic radius decreases due to increased effective nuclear charge.
2. Down a Group (Top to Bottom): Atomic radius increases due to the addition of electron shells.

Step 2: Key Formula or Approach:

To compare atomic radii, we use these periodic trends:
• Across a period, atomic radius decreases.
• Down a group, atomic radius increases.

Step 3: Detailed Explanation:

Let's locate the elements:

Period 2:
N (Group 15), F (Group 17)
Trend: radius decreases from left to right.
So,
N > F
or
F < N

Period 3:
Na (Group 1), Si (Group 14), P (Group 15)
Trend: radius decreases from left to right.
So,
Na > Si > P
or
P < Si < Na

Comparing Period 2 and Period 3:
Elements in Period 3 generally have larger atomic radii than elements in Period 2 because they have one extra electron shell.

So,
F, N < P, Si, Na

Combining all the orders:

Smallest to largest:
F < N < P < Si < Na

Step 4: Final Answer:

The correct increasing order is:
F < N < P < Si < Na.