Question

Atomic radii of fluorine and neon in angstrom units are respectively given by?

• A. 0.762, 1.60
• B. 1.60, 1.60
• C. 0.72, 0.72
• D. None of these values

Answer 1

The correct option is A

0.762, 1.60

This is a completely memory-based question, but you could eliminate 2 of the values knowing that Fluorine and Neon have different sizes. But you might expect Neon to be smaller than Fluorine according to the trend along a period.

The reason for the larger size of Neon:
The noble gas atomic radii are measured a little differently than all of the other atoms in the periodic table. For everything that's not a noble gas, we use average bond lengths as a measure of how big an atom is. Fluorine has a small radius because it tends to form short strong bonds.

Noble gasses don't usually form covalent bonds so their atomic radii are usually their Van der Waals radii which are generally much larger.