Question

The correct order of atomic radii of given elements is

• A. \( {B}<{Be}<{Mg} \)
• B. \( {Mg}<{Be}<{B} \)
• C. \( {Be}<{B}<{Mg} \)
• D. \( {B}<{Mg}<{Be} \)

Hint:

When comparing atomic radii, remember that atomic radius decreases as we move from left to right across a period and increases as we move down a group.

Answer 1

The Correct Option is A

The atomic radius of an element is determined by the distance between the nucleus of an atom and the outermost electron shell. Let's evaluate the options by considering the position of each given element in the periodic table and the general trends of atomic radii.

Periodic Trend: As we move across a period from left to right in the periodic table, the atomic radius decreases due to the increase in the effective nuclear charge which pulls the electron cloud closer to the nucleus. Conversely, as we move down a group, the atomic radius increases because additional electron shells are added.

Analysis of Elements:

• Boron (B): Located in group 13, period 2. Being in the second period, it has a relatively small atomic size.
• Beryllium (Be): Located in group 2, period 2. Slightly larger atomic radius than Boron but still small because it is in the same period as Boron.
• Magnesium (Mg): Located in group 2, period 3. Since it is in the third period, it has a larger atomic radius than both Boron and Beryllium because it contains an additional electron shell.

Conclusion: Based on the periodic trends, the atomic radii increase as you move down a group. Thus, the correct order of atomic radii is:

\(B<Be<Mg\)

Answer 2

The atomic radius generally increases as we move down a group in the periodic table due to the addition of more electron shells. However, when comparing elements in the same period, atomic radius decreases from left to right across the period due to increasing nuclear charge, which pulls the electrons closer to the nucleus. - Boron (B) is in Group 13 and Period 2.
- Beryllium (Be) is in Group 2 and Period 2.
- Magnesium (Mg) is in Group 2 and Period 3.
Now, comparing their atomic radii:
- Beryllium (Be) has a smaller atomic radius than Boron (B) because Be is a Group 2 element, and Group 2 elements generally have smaller radii than Group 13 elements in the same period.
- Magnesium (Mg) is further to the right in Period 3 and has a smaller atomic radius compared to Beryllium (Be).
Thus, the correct order of atomic radii is: \[ {B}<{Be}<{Mg} \]